Camp Prackness July 22d 1780
Considering the nature of the construction of the British Works at New York, we ought to conclude that such a place is capable but of avery short Defence, if we were not obliged to make some allowance for the number of its Garrison. Experience has proved that when a Town is regularly Fortified the approachers of the Beseigers can be carried on as far as the Top of the Glacis in about fifteen days, if the Beseiged have no mines under the Glacis, and the Ground is not of a Nature too difficult to be Dug. we may conclude that Space of time to be employed in approaching the British Works to the cage of their Ditches, because if the Enemy can disturb our workmen by their Sallies, we shall not suffer as much by thier fire as we should do in the attack of a regular Fortifications. In acting against New York we have many advantages which we should not meet with, if their Works were regularly constructed.
1st as they have no covered way, the Faces of their Works must be discovered from a great distance, and our Batteries established at 300 yards from them can be Battering Batteries, so when we shall have carried on the approaches as near as the out side of the Ditch it is possible that the Works should be ruined so much that they could be immediately Stormed, without being obliged to erect New Batteries there for that purpose.
2dly Their Ditches being not walled, nor very deep nor very wide, and not directly defended, we shall not be obliged to make a Subterraneous descent to get in them, and an epaulment to cover our people in crossing them to Storm the works, those two operations are always very long.
3d Their Fortifications consisting of but one line, we shall not have out Works to attack, which takes always a long time to be battered, one after the other, to make the necessary dispositions to Storm them, and to make entrenchments to keep possession of them when they are carried, besides that those Works cost always a great many men to the Beseigers, their attacks being made under the fire of the Flancks and Faces of Bastions.
4th The works of the Enemy being small, they will not have a place sufficient in them to make an Entrenchment, to keep possession of one part of the Work, when the other will be taken, and by that means oblige us to make another attack on that entrenchment.
An other advantage which is immense, is that the Enemy having but one line at each place, the first work carried is one of their main ones, there is no hope left for them, and no prospect of a further Defence.
It is natural to conclude from what I have said before, that there is no comparison between the Attack of a regular Fortification and that of New York; either for time or loss of Men. the most difficult will be to make the approaches with care, and precaution, on account of the number of the Garrison, we shall be obliged to have our Flancks secured by Works of good defence, and the head of the approaches always carry’d on always under the protection of parts finished, and fit to receive strong Guards.
About Sixty or Seventy peices of Cannon with Twenty Mortars, or Howitzers, are wanted for the Attack of a line of Fortification composed of two Bastions, having three half moons, entrenchments in the place of arms of the covered way, with three lunettes on the front of the Glacis. besides those above mentioned peices there is commonly some collateral ones, which are not to be taken, but as they furnish cross fires and of rivers on the approaches, they must be battered by ricochet to dismount their cannon, as those of the peices to be attacked if for so many works we should want about Seventy peices, we may estimate that Forty peices should be sufficient for the attack of the Fortifications on York Island composed of redoubts joined together by a line.
The works of the enemy being in a straight Line, we can establish our batteries on the prolongations of their Faces to beat them by ricochets but when we shall be very near and besides that, those faces being very short, the ricochet will have but little effect upon them. To that the best way to dismount their cannon is with Shells, and on that account we shall want Twenty Mortars or Howitzers. if we should not be in possession of the river, it will be necessary to have some more to keep off the British Ships, if they come up to fire on our Flanks, and take some rivers on our approaches.
A Front of a regular Fortification such as the above mentioned, is able to make a defence of about Forty or fifty days, and the Quantity of ammunition wanted for its attack, is two thousand rounds for each cannon, and one thousand shells for each mortar but on account of the difference between the Said fortification, and that of New York it appears that [one] thousand rounds will be sufficient for the Cannon for our attack, and as we will derive great assistance from our Mortars we must have the same number of Shells to each of them.
If the British should repair the Works they had across York Island, near Harlem, we should want at least as much time and ammunition for this attack, as for that of the Line of Fortifications ne[ar] New York and the second attack could not go on as fast as the first, because it is to be supposed that our Men being wearyed could not Work with the same ardor.
The Strength of the Enemy will oblige us to Fortify every position we shall take on York Island, especially if the Enemy are in possession of the river, each of those positions will take three or four days to be put in order of defence, before we begin the attacks and it will be necessary to have fifteen twelve & nine pounders for their defence.
I know nothing of the British Works, but by reports and am not certain how far I may depend upon them.
Lt Col. of Engineers
DLC: Papers of George Washington.