From Brigadier General Duportail
White Plains 13th [September]1 1778
Memoir on the works made in the Highlands
The works, which are in hand at West Point and some inconsiderable ones, which it is necessary to add to them, will, with the help of the chain, perfectly fulfil the object which is proposed, that of hindering the enemy’s remounting the North River.
Fort Putnam, which is, as it were, the key of all the others may be rendered almost impregnable. There is indeed a height, which commands it, but besides that this height may be taken possession of with a redoubt, it would be very difficult for an enemy, even when master of it to bring heavy cannon there. Besides it would be too far to make a breach. This fort has nothing to fear, but a bombardment, or escalade. with respect to a bombardment, the mean to render it ineffectual is to have bomb-broofs sufficient for three fourths of the Garrison, magazines hospital &c.—I am told Col: Koshiusko proposes, at this time to begin one; but which will not suit more than 70 or 80 men. This is far from sufficient. There must be another, the place and size of which, I have pointed out to the Captain who conducts the works. It will contain about two hundred men—with respect to the escalade, to prevent its success, the side of the fort which looks towards the river and is the most accessible, as well as that which looks towards Fort Arnold, must be raised a great deal more than it is, and besides the palisades and chevaux de frises, abaties must be made in front. The roof of the great bomb-proof, which I propose, may be made use of to collect the rain and conduct it into the Cistern. This will always be a small resource.
Fort Willis2 does not appear to me well traced. It ought to be put entirely upon the declivity which looks towards the River, the face next Fort Putnam following the ridge of the eminence. In this manner, it would have overlooked equally all the valley between Fort Putnam and itself and all its interior would have been under cover of Fort Putnam; the face next the river would have extended to the very border of the declivity; and the work in every respect would have been a great deal stronger. In its present position it is too large its parapet makes too great a circuit. It will be best perhaps to rebuild this fort altogether; if this is not done, to remedy its inconveniences, the face opposite Fort Putnam must be raised not so as to cover the interior, which I am told Col. Kosciousko proposes, because it must be prodigiously elevated to answer that purpose—3 but instead of this, I would prolong the eminence which is in the middle of the work, and improve it into a Traverse, to extend the whole length of the work—I would then reject a third of the work on the South, as altogether useless—the bomb-proof will be backed by the traverse abovementioned.
I should have prefered to the Redans which are in front of the Redout Willis, on the south side, and which require for their defence four or five hundred man—a small inclosed work to secure the possession of the eminence and protect the batteries in front—but for the present, matters may be left as they are.
Fort Arnold appears to me to be pretty well situated and traced—but if the intention of Col. Kosciousko is to leave the sides next the River at the present height—(as appears to be the case) I cannot approve it—they are exceedingly liable to an escalade—it is proper to elevate them, and even to make a small covert way without, having good palisades in front, to secure the body of the place against all Surprise.
The Scantlin for the Bomb proofs appears to me too feeble—the top will be almost flat—What is made of earth ought to have been of Masonry or bricks—however I forbear enlarging upon this subject, because time will hardly admit of a Remedy—the Stuff being Squared, and ready to be put together—observing only that the work should be sunk more in order to furnish a greater thickness of earth for the roof.
There is below Fort Putnam,4 a battery nearly round, which is extremely well placed for battering the Vessels which should approach the Chain—but its situation likewise exposes it to the fire of the Ships—at least as it is much advanced, the fire of the tops would injure the Gunners, and the more, as by the form of the battery they are collected within a very small Space—it appears to me advisable, to raise the parapet of this battery several feet—and to cover the embrasures from the top of one Merlon to another—so as not to interfere with the working of the Guns—altho it is equally necessary to secure the Chain on the left-hand Shore of the River—it seems to have been little attended to—there is no enclosed work on this side to hinder the enemy from debarking a sufficient number of men to get possession of the ground and cut the Chain. there is only a battery which may answer some good ends—but cannot prevent the enemy from doing as abovementioned—With three small works we shall render this point perfectly secure—the first to be place⟨d⟩ where the block house of fort independence stood5—it is sufficient for it to contain abou⟨t⟩ sixty men—its end is to afford an immedia⟨te⟩ defence to the Chain and its extremity—against a hardy enterprise, which a few men are engaged sometimes to undertake by dint of money or other recompences—the parapets ought to be of wood in order to take less room—and sufficiently elevated to cover the area.
the second Redout should be placed on a steep eminence which commands all the other rising grounds in the island.
the third on an eminence in the rear of the newly constructed battery—these two Redouts ought to be made for 150 men or 200 at most.
There was a battery, the remains of which are still in existence, (below Fort Independence)6—it was perfectly well placed for battering the enemys Ships—it ought to be rebuilt, with a strong parapet of earth—and as this battery is low and exceedingly exposed to a plunging fire from the Tops of Ships—the parapets must be high, and terminated by a Roof of thick plank for the protection of the Canoniers—this battery as well as that which is just finished, will be interlocked by the three Redouts—and be in perfect safety—With these works we shall be completely masters of the Island.
As to the Chain itself, I would not have it floating on the Surface of the Water—which exposes it to be laid hold of by machines prepared for the purpose, on board the Vessels that may approach—but the greatest danger arising from this would be the breaking it by Cannon Shot—when a vast number comes to be fired on both sides in a contest between the enemys Ships and the batteries—I should think it more eligible therefore to suspend the Chain three feet below the surface of the water—because as the greatest number of the Shots bound when they strike the water—there would be so many ineffectual with respect to it—besides, the matter would be very easily executed—by placing the floats above instead of below the Chain—and having another chain made fast at each end to the great one, and carried above the floats—by these means the great Chain may be supported at the depth which is judge⟨d⟩ suitable—if a shot should carry away the Chain, by which the great one is made fast to the floats—the whole mischief that would result, would be, that the Chain in that place would douse a few feet more.
There are so many accidents by which an iron Chain may be broken, that it would be prudent to have a stout cable in reserve to supply its place in part, for a time.
Every thing that I have explained being finished—1800 men will render us completely masters of the River, and put us out of reach of the enemys enterprises—At least, the Resistance that may be made will allow ample time for the arrival of Succours, however remote the Army may be.
The following is the Distribution of these troops as nearly as can be judged—
|In Fort [Arnold]7||700|
|Small Work above Fort Putnam||100|
|For the Works on the Island or|
|Peninsula, on the left-hand Shore||400|
At the present moment, if we except the batteries against Ships—the works are not in a state of defence—but a little time would be sufficient for completing fort Putnam, which is the most important—the Redouts on the island on the left-hand Shore—are likewise objects of the first attention.
His Excellency had ordered me to give him an account of the expences arising from all these works to the present time—it is not in my power to present any thing on this subject, not having seen Col. Kosciousko, who alone is possessed of these facts—I am going to write to him for this purpose.
I was likewise at New Windsor—The River appears to me very wide in this part for a defence of Chevaux de frise—besides the Chevaux de frise themselves appear to me to be very weak—and I can with difficulty persuade myself, that a Ship would be much embarrassed by them—And indeed until West point is completed—I do not think we should occupy ourselves about New Windsor—I shall therefore forbear adding any thing farther relative to it.
Translation, DLC:GW; ADS (in French), DLC:GW. On a separate scrap of paper following the translation is written a related text that does not appear to be translated from the French; it reads: “One hundred pieces of Cannon—(twenty fours and eighteens) including those already here—will be wanted.
“The number of Artillery men—exclusive of the eighteen hundred men required to garrison the Forts & man the works—may be estimated at Six Hundred.”
1. The month is taken from the docket on the translation. Although the French text is dated “13 aout,” 13 Sept. is almost certainly the correct date. Duportail was ordered to undertake a survey of West Point defenses on 27 Aug. and arrived there on 9 Sept.; his report was delivered to GW before 19 September. Moreover, John Laurens, who translated most of the document, was in Rhode Island on 13 Aug. and remained there until early September.
2. In this and subsequent references to “Fort Willis” or “Willis Redoubt,” Duportail may have meant Fort Webb (see Miller, Lockey, and Visconti, Highland Fortress description begins Charles E. Miller, Jr., Donald V. Lockey, and Joseph Visconti, Jr. Highland Fortress: The Fortification of West Point during the American Revolution, 1775–1783. West Point, N.Y., 1988. description ends , 130).
3. The text preceding this note is in Alexander Hamilton’s writing, but the remainder of the translation is in John Laurens’s writing.
4. Duportail probably meant Fort Arnold (see also note 7).
5. Duportail wrote “fort de l’independance,” but he was apparently referring to Fort Constitution.
6. Duportail was evidently referring to Fort Constitution.
7. Laurens originally wrote “In Fort Putnam,” which agrees with the French text, but he crossed out “Putnam” and added a note that reads: “fort Arnold probably.”