Memoranda relative to the lines thrown up to cover Lisbon in 1810

Preface

. The following Memoranda contain a por tion of the ten sheets which the author deemed it right to withdraw from the se cond edition of the " Journals of Sieges," in consequence of a military force being sent to Lisbon at the moment of their being printed. These Memoranda were originally drawn up with the view of making known to those who had not the opportunity of personal inspection, the nature and extent of the defences created to cover Lisbon. They are now distributed with the same view; and if they prove useful to any brother officer seeking professional information, the writer will consider himself well re paid for the trouble of extracting them from his ndles. Il est des militaires qui demandent a quoi servent les places fortes, les camps retranches^'art de l'ingenieur; nous leurs demanderons a notre tour coinment il est possible de ma neuvrer avec des forces inferieures ou egales sans le secour des positions, des fortifications et de tous les rnoyens supple mentaires de l'art. — Conversations de Napoleon, par Montholon.

Chapter I

The retrenched positions covering Lisbon, known under the denomination of the Lines of Torres Vedras, have gained so much celebrity, as having formed the barrier from which the tide of French conquest first receded, and moreover possess so many peculiarities of defence, and are so free from the objections usually urged against lines, that some observations on their nature, construction, and mode of occupation, can scarcely fail to be interesting to professional and other officers seeking military information ; and happily, since the first edition of this work was penned, in 1813, the affairs of Europe have so changed as to admit of some degree of descriptive detail being with out impropriety substituted for the former eulo gium of the general merit of the lines. The determination to commence these works may be dated from the battle of Talavera.

The offensive movements which led to that action B having put to the test the value of Spanish co operation, and having fully demonstrated the utter inefficiency of their armies, from want of organization, want of discipline and skilful officers, it became apparent to the Duke of Wellington that the contest would, in the next campaign, devolve on the small body of veteran British and newly raised Portugueze troops under his command, and a defensive system of warfare ensue. To prepare for a final struggle was thenceforward the great object of consideration; and as the hope of successfully defending an extended and open frontier, like that of Portugal, against a very superior and highly skilful enemy, could scarcely be entertained, it was decided to seek out some position in the lower part of Estramadura, not liable to be turned or passed, and having an assured com munication with the sea, which should com mand all the approaches to Lisbon, and which position, being retrenched in the strongest manner, would offer a point of concentration for the whole of the defensive forces of Portugal, army, militia, irregulars, &c. where they might, in conjunction with the British, be victualled and supplied with ammunition for any period of time, whilst occupying a most favourable field for deciding the fate of the capital and the king dom in a general action.

With these views, whilst the army was can toned on the Guadiana, Lord Wellington, in the month of October, 1809, attended by his quarter-master-general, Colonel Murray, and his chief engineer, Lieutenant-Colonel Fletcher, made a personal reconnoissance of the country in front of Lisbon, and judging the scheme practicable by means of a chain of fortified posts to extend across the peninsula, directed the officers of engineers to examine and minutely delineate the various strong features of ground between the sea and the Tagus, on a breadth of several miles, in order to enable him to decide on the most eligible line of defence whenever he should deem the moment arrived for commencing the work. In the meanwhile the defences of Fort St. Julian at the mouth of the Tagus were to be extended to cover and ensure a communication with the fleet ; and ground was to be occupied as retrenched posts or positions at Castanheira, Monte Agraca, and Torres Vedras, to support the manœuvres of the army while retiring on the meditated line, or place of embarkation.

(1) These labours proceeded uninterruptedly till the commencement of February, 1810, when, the preparations of the French for the conquest of Portugal having assumed a decided charac ter, Lord Wellington, during the march of his army from the Guadiana to the Coa, revisited B Lisbon to give final orders respecting the works to be erected for its protection. A few days were sufficient to ride over and decide on the ranges of hills convertible to his views; and having fixed the principal points and grand outline of his defensive system, he rejoined his army on the frontier, leaving the plan, trace, and execution of the works to Lieut. -Colonel Fletcher, whose sound military knowledge and indefatigable zeal were pledges for the details being worthy of the design. At this time it was presumed that the in vading army would be nearly double the strength of the defensive force, and equal to manœuvre, in two formidable bodies, on the right and left of the Tagus, so as to throw back their oppo nents hastily on Lisbon; or, if parried in stra tegy, likely to attempt wearing them out by a succession of sanguinary combats.

Expecta tion of a successful resistance was therefore very doubtingly entertained, and the object of primary interest and attention was to secure places for re-embarking the army in case of disaster, or if the enemy should advance before the lines could be rendered of sufficient strength to make it prudent to occupy them. The next consideration was to establish such strong1 en closed works to block up the passes as should enable indifferent troops to delay or check a hostile column, in its endeavours to interrupt the retrograde manœuvres of the regular army; and these paramount objects being attained, every effort was to be used to strenghten the selected ranges of hills to the utmost that time would admit. From the rocky nature of the coast of Por tugal, there are very few spots favourable for maritime communication; and in the space to be covered by the projected lines, only one suitable point could be found, being a small bay, not two hundred yards in length, and very par tially sheltered from the ocean by Fort St. Ju lian at the mouth of the Tagus; and even at that spot, at intervals, such a sea rolls in for days together that no boat can with safety approach the shore.* The works to cover an embarkation were therefore to be traced of a threefold nature : first, to form a position of such extent that the * Even in the advanced season, between the end of April and middle of June, 1810, at the large fishing town of Ericeira, such a surf prevailed that the boats could not be launched for a single morning.

In 1811, four jetties, to cover the place of embarkation at St. Julian, were constucted by Captain Holloway, at an ex pense of ,£15,000, which, notwithstanding every local and nau tical opinion being unfavourable to their stability, resisted the most furious gales of wind throughout the war, and rendered an embarkation practicable in all seasons and weather. whole army might sustain itself and protect its artillery and stores, during any period of bad weather which might retard the commencement of the embarkation ; secondly, with an enclosed work within the principal trace, of such size and strength as might admit of diminished numbers defending themselves, should a gale of wind come on after one portion of the troops had been embarked; or should the army have met with such severe loss on its retreat, previously to reaching the point of embarkation, as to preclude the possibility of occupying the outer line; and lastly, with a small post on the shore sufficiently strong to protect the rear guard, and ensure its safe embarkation.

The first object was obtained by means of a line of detached redoubts and intermediate de fences, appuying its tight on the Tagus, near Fort das Maias, and its left on the ocean behind the canal at the little fort or tower of Junquiera. The works of this exterior line commanded the town of Oeyras, and included within their trace, the contour of which measured 3,000 yards, the whole promontory, at the extremity of which stands Fort St. Julian. The second was effected by the construction of a large irregular enclosed work, occupying the summit of the height im mediately in front of Fort St. Julian. The last object was found in Fort St. Julian itself, which, from its extravagantly high scarps and deep ditches, can never be successfully assaulted against the slightest opposition. As a secondary point of embarkation, and looking to the probability of a series of operations terminating on the left of the Tagus, a line of works was to be thrown up at Setuval, to cover the right bank of that harbour, and keep open its communication with the sea.

These works were to be formed partly of a con nected trace and partly of detached redoubts, their right being closely supported by Fort St. Phillippe, and their left resting on a scarped cliff. The front of defence rather exceeded 1,500 yards, and, besides occupying the ground most favourable for the erection of batteries to annoy the transports, formed, with Fort St. Phillippe, a strong post, in which a division might maintain itself during the embarkation of the main-body of the army, and ultimately effect its retreat by the sacrifice of a small rear guard in the Fort. The principal line of defence, denominated subsequently the second line, was formed on the knowledge that only four great paved roads lead to Lisbon, between the sea and the Tagus, below the point where that river from its en creased depth and breadth becomes, in a military sense, impassable to an army — that three of those roads, at nearly parallel points, pass over or between heights of extraordinary strength, viz. at the passes of Mafra, Monta chique, and Bucellas, and that the fourth, bordering on the Tagus where the ground is less bold, passes under a strong range of heights at Alhandra, nearly two leagues in advance of the right of the above mentioned line of passes; and further, that the country between the paved roads being hilly and broken could not, without the utmost delay and difficulty, be crossed at any part by an army with its artillery.

It was proposed to block up the passes with formidable works, and to support their defence by forming the different ranges of heights between them into one uniformly strong line, so as to ensure a connected barrier across the peninsula, which an invader must force through by a front attack before he could reach Lisbon. Nature had done much in aid of this design: commencing on the left from the sea at the hamlet of Ribamar, in front of Ericeira, and following up the course of the little river St. Lorenzo to Cacheca, adjoining the pass of Mafra, a distance of seven miles, a deep, rugged, and in many parts impracticable, ravine leaves scarcely a favourable point for a battalion to advance in column. This flank therefore presents no inducement whatever for an invader to select it for his principal line of operations, and it was considered that, in the first instance, the destruction of the peasants' tracks, and establishing artillery in secure enclosed works, 88 to 94, on the projecting points, to flank the most accessible part of the ascent, would be sufficient to enable a small corps of observation to secure this portion of the line till reinforced.

The pass of Mafra was strengthened with pe culiar care, and considerable labour; for although the main ascent, viewed as an isolated feature, possesses great strength, there is much ground on its right enclosed with a wall as a royal park (tapada), the features of which are but very moderately bold; and moreover two roads run nearly parallel to the northern and southern boundaries of the tapada, which offer great fa cilities to an enemy to manœuvre and carry the pass by a flank attack. The main ascent being rendered secure by means of redoubts and emplacements for artillery, so disposed as to enfilade the road and concentrate their fire upon points of it where deep and broad cuts, and other artificial obstructions, were marked out to be formed at the required moment, the prin cipal labour was directed to secure the flanks of the pass.

The wall of the tapada, or royal park, had a banquette added to its interior, and efficient flanks were created along its front, either raised for field-pieces or loop-holed for musketry; and a chain of redoubts, 74 to 77, was thrown up on the most commanding points within the enclosure, to sweep the ravines and interdict the passage along the road in its rear. Further, each feature of the ground overlook ing the approach to the tapada was occupied by a redoubt, well furnished with a powerful and commanding artillery, 62, 63, 64. The strong heights above Gradil, called the Serra de Chypre, so situated on the road from Torres Vedras as equally to obstruct the march of a column by the main pass of Mafra and the col lateral branches on the left of Morugueira, was also strengthened to the utmost, by redoubts 78 to 81.

A little in rear, and to the left of the village of Morugueira, works were established, 82, 83 and 84, for the defence of the minor pass by Cacheca, and as a communicating link of the chain be tween Mafra and the left extremity of the line. Further, to guard against these important points being turned with artillery on their left, and that the security of the strong corps likely to be allotted for the defence of the main pass of Mafra should not be altogether dependent on a successful defence of the extensive line of the ravine between Morugueira and Ribamar, a retired post was established at Carvoiera, on the left of the Chilleros valley, 96 and 97, to command the only coast road from Ericeira to Cintra, St. Julian's and Lisbon, in its descent of the opposite bank of the valley; and that road where most under fire of the redoubts was to be mined for destruction.

No. 95, situated on a strong feature of ground on the right of the valley, co-operated in these objects. Lastly, the town of Mafra itself was formed into a defensive post towards Ericeira, and was covered on that side by a chain of works, 85, 86, 87, blocking up the only lateral approaches practicable for artillery. The next object of attention was the pass of Cabeca-de- Montachique. The heights forming the immediate flanks of that pass being naturally as strong and favourable for defence as can be desired, little labour was bestowed on them, and the principal consideration was to block up the road. For this purpose twenty-five pieces of artillery were secured in redoubts (No. 52 to 61 inclusive), situated on strong features, mostly in advance of the principal range of heights to the right and left of the great paved communication from Torres Vedras and from So bral through Zibriera, which, completely enfila ding a considerable length of the approach, were considered to render a direct attack along the road hazardous in the extreme.

This disposition of the redoubts was caused by the advanced features of the ground intimately connecting with each other, and being deemed to form a chain of posts collectively stronger than the main features of the pass. It is, however, an example of fortifying to be followed with great caution, it being contrary to all just principles of defence, to extend a chain of small posts in advance of a main feature — that is, to court an action in detail, and is utterly inadmissible in the defence of a pass, wherever the approach is such that an enemy can act off the great road. The defensive features of the country, from the pass of Mafra to that of Cabeca-de-Mon tachique, are less distinctly marked than along any other portion of the line ; but the hills, though not continuous or precipitous, are high, steep and salient, affording the means of covering a parallel road which connects the two passes.

These hills were occupied by isolated redoubts, 62 to 73, overlooking the difficult country in their front, commanding every approach to the lateral road, and securing that communication to the defenders— they were consequently both outposts and guards to a chain of rather formidable heights in rear of the road ; and which heights thus covered were con sidered to offer a favourable field of action, should an enemy think it worth while to attack a re-entering line, from whence only one in different road for artillery exists to facilitate his further movement, and against which artillery could only be brought by previously forcing the works near Gradil (Serra de Chypre), or the advanced defences of the pass of Montachique. From Montachique to the pass of Bucellas the heights are of a nature to preclude the necessity of works, except for the purpose of blocking up a road for cavalry, and perhaps cars, over the ridge at Freixal, which was effected by retrenchments, 49, 50, 51.

The pass of Bucellas is of the strongest de scription, the road running between two high and steep mountains, through an opening of only a few hundred yards : the defence of the pass consequently hinged on the troops main taining possession of the flanks of the mountains, and all an engineer could do was to establish secure emplacements for artillery to enfilade the pass, to mine the bridge at its en trance for destruction, and create other ob structions on the road to detain the advancing" columns under their fire. The approach was thus guarded by works, 43 to 47, and in case of disaster 45 was intended to cover the retreat of the defenders. From the pass of Bucellas towards the Tagus, the Serra de Serves, a high and extremely diffi cult ridge with scarcely any break, occupies a front exceeding two miles to the road, which crosses it from Villa de Rey.

Its right flank then overlooks and gradually falls on the low ground bounding the Tagus. This space of two miles and a half between the right of the mountain and the river, presented full scope for art and labour, and advantage was taken of every feature of the ground to give it strength. Works were multiplied along its centre, No. 34 to 39, in front of Via Longa, and also on the bluff extremity of the Serra de Serves, above Portella, 40, 41, and 42, forming its left flank. Its right flank, resting on the Tagus and closed by a strong redoubt, No. 33, it was proposed further to secure by deep and broad cuts through the salt-pans in its front, made in a direction to be enfiladed by the fire of gun boats ; but notwithstanding all the labour thus bestowed on this portion of the line, it was confessedly much the weakest, and great de pendence was placed on the aid it would derive from a peculiar chain of strong heights, forming almost an isolated feature, about five miles in its front, at Alhandra.

These heights it was proposed to dispute with an advanced corps, and works, 1 to 4, were established to enfilade the main road, flank the low ground, and equalize the strength of the front ; and re doubts, 5, 7, 8, were thrown up as impediments to the position being turned with artillery. The above mentioned features of country (occupying 22 miles of front) thus connected and strengthened with 59 redoubts, mounting 232 pieces of artillery, and requiring 17,500 men for their garrisons, formed the principal line of defence across the peninsula, and fulfilled all the conditions sought for in a position to cover Lisbon. The works which, under the first view of the army retiring into Estramadura, had been thrown up on the heights of Torres Vedras and Monte Agraca, 14 to 17, and 20 to 27, served as valuable outposts to this defensive line, from six to nine miles in its front, blocking up the principal approaches, and assuring the troops time to take up their ground and occupy the new defences before they could be attacked in force.

These advanced works were completely isolated posts, except that the country on the left of Torres Vedras being open, and offering an inviting facility to an enemy to turn that defile and the works for its defence, the pas sage of the little river Zizandra was guarded or rather watched by three redoubts established on its left bank at St. Pedro de Cadeira, and in rear of Ponte de Rol, 30, 31, and 32 ; and with the same view, as respects Monte Agraca, redoubts 9 to 13 were thrown up in the pass of Arruda. Two strong isolated features of ground which command the main roads at the intermediate points of Ajuda and Enxara dos Cavalleiros were also retrenched, Nos. 18 and 19 — 28 and 29, as additional impediments to the rapid ad vance of an enemy on the principal line. Signal posts for the purpose of instant com munication between these various detached works, and generally along the whole front of defence, were established on the points best uniting an extensive view with perfect security.

Lisbon, the prize to be disputed, situated twelve miles in rear of Via Longa, fifteen miles in rear of the pass of Bucellas, twelve in rear of the pass of Montachique, and twenty-three in rear of the pass of Mafra, is of great size, and advantageously placed for defence and sub sistence on the right bank of the Tagus. Its buildings are of such an incombustible nature as to render bombardment almost harmless ; and the approaches being generally narrow and sunken, and flanked by stone houses having the doors and windows secured with iron °rating;s, and other defensive expedients, render the suburbs peculiarly susceptible of an irregular defence. It was not therefore deemed necessary to fortify the enceinte, but the Portugueze were encouraged to erect barriers and traverses at the several entries, to create interior posts, to mount guns on the castle, the Peha convent, and other domineering and strong points ; and by their exertions the city was expected to be placed altogether beyond a coup-de-main when occupied by such forces as it was intended at the moment of danger to throw into it.

St. Julian, the point of embarkation in the event of defeat or discomfiture, is situated twenty-four miles in rear of Carvoiera, and twenty-seven miles in rear of the pass of Mafra ; the high road to it from the other passes being through Lisbon, though it may be reached from either of them by tolerable cross-country com munications without passing through that city. These extensive works were pressed forward by Lieut. -Colonel Fletcher and his officers with the greatest zeal and ardour, and they were liberally supplied with means. A detachment of infantry was selected to act as overseers, di rectors, and artificers; two regiments of Por tugueze militia were allotted as pioneers, the peasantry of the surrounding districts were put into requisition as labourers, and no petty cavils about official forms of expenditure were allowed to impede the supply of materials and stores.

(2) c Napoleon had proclaimed early in the year, with more than his usual arrogance, that he was collecting a force of 110,000 invincibles on the frontiers of Portugal to drive the English out of the Peninsula ; and it was naturally concluded that he would act at least with his wonted celerity and enterprize — that he would push forward to the main object, regardless of isolated fortresses, and strike a final blow before means of resistance could be matured. The several works of the lines were in conse quence thrown up in haste, and of a construction requiring the least labour, compatible with a certain degree of strength : the redoubts were generally made of a field profile of a size to require from 150 to 250 and 300 men for their defence, and were armed, according to the im portance of their fire, with three, four, five, or six pieces of artillery.

The main works at Torres Vedras, Monte Agraca above Sobral, and Oeyras, being con sidered independent forts, or rather species of petty fortresses, were made larger and stronger than the works at other places; particularly those of Torres Vedras, which blocking up the most direct road to the point of embarkation, and being moreover on the spot of former en terprises, were regarded with peculiar jealousy : they were of a trace to be tolerably flanked, and of a magnitude to require a garrison of 2,200 men with 40 pieces of cannon, independently of the number required to guard the lines of com munication with the convent of St. Joa, and the castle in the town, which latter were formed into good posts, Nos. 25 and 27, and mounted with seven pieces of artillery. The main work on Monte Agraca, which was made roomy and spacious, required a garrison of nearly 1,000 men, and was armed with 25 pieces of ordnance; it was, however, very im perfectly flanked, and the profile was almost the same as that of the small redoubts.

In ad vance of this main work, at various points of the ridge, the dependent redoubts, 15, 16, 17, mounting 19 guns, and requiring above 1,000 men for their defence, (the whole being con sidered to form only one post, occupying the summit of Monte Agraca,) were thrown up to flank and see the ascent. The inclosed work on the height between Oeyras and St. Julian's was sufficiently flanked, and of a magnitude to require a garrison of 1,340 men, and on it and its dependent redoubts and batteries above 50 pieces of ordnance were mounted. The above-mentioned three principal works were furnished with 160 rounds of ammunition per gun, thirty of which were grape, and 200 hand grenades: the other redoubts were supplied with 60 rounds per gun, eight of which c were grape shot, and from 12 to 16 hand gre nades each.

The artillery mounted in the several works were 12, 9, or 6 prs. with two or three 5§ inch field howitzers in the larger forts; they were all Portugueze iron ordnance, on carriages of a most primitive construction, with such low trucks as to be perfectly immoveable over broken ground, and consequently not to be immediately rendered useful to an enemy on carrying a redoubt. The artillery of every work, being mounted with the view to guard some fixed object, fired through embrazures. It has been stated that the works of St. Julian,* Monte Argraca,f and Torres Vedras, £ were the first commenced in the autumn of 1809, as isolated points, with the view of having some defence prepared for the army, should the invaders instantly advance as they threatened. The works for the defence of the passes were next undertaken, § and ultimately, in the spring of 1810, the whole were in progress.

With * On the 3d November, by Capt. Wedekind. f On the 4th ditto, by Capt. Williams. X On the 8th ditto, by Capt. Mulcaster. § Viz. Mafia, on the 17th Feb. by Capt. Ross; — Ericeira and Carvoiera, 19th Feb. by Lieut. R. Jones; — Montachique do. Capt. Mulcaster; — Via Longa, 24th Feb. Lieut. Stamvay; — Arruda, 17th March, Lieut. Forster;— Ponte do Rol, 2Gth March, Lieut. Thomson. the same feeling the works at St. Julian's were originally confined to the heights between the fort and the town of Oeyras: in the spring, and early in the summer of 1810, the advanced line of redoubts 103, 104, 105, 106, 107, 108,* was thrown up; and in the autumn, the ex terior points were occupied, and the advanced defences completed.f Such was the original plan and construction of the lines which, when nearly brought to the degree of perfection that the aspect of affairs seemed to admit, were given over to the charge of Captain John T. Jones, by Lieut. -Colonel Fletcher, on the 6th July, 1810; and the ad vance of the invaders being momentarily ex pected, himself hastened to the scene of active operations on the Coa.^ * Principally by Capt. Squire. *f- It will be seen from the above dates that, except at Monte Agraca, a point quite out of the beaten track, and almost un known to the British, the works of Torres Vedras were under taken three months before any other part of the lines, which ac cidental circumstance, added to the previous celebrity of the pass, caused their name to be given to the whole system of defence.

X " COMMANDING ROYAL ENGINEERS' ORDERS. " Mafra, 6th July, 1810. "As Lieut.-Colonel Fletcher, Captains Chapman, Squire, and Goldfinch are about to join the army, Capt. Jones will be left in the immediate command and superintendence of all works It would appear that, soon after Col. Flet cher's arrival at Lord Wellington's head-quarters, the proposed mode of occupying the lines underwent consideration, and some change was contemplated, (probably in consequence of the invaders engaging in the siege of Almeida, which gave expectation of the rains commencing pre viously to the final struggle, which, as will be hereafter shown, would materially change the relative strength of some portions of the counand duties connected with the Engineer Department in this part of Portugal, and he is therefore to be obeyed accordingly.