If Great Britain had not called continental auxiliaries to her aid in 1776, her disposable force for colonial service would have been less than half of the army of Washington.
Until the fortification of Brooklyn and New York had been well advanced, the British ministry had not been able to assign even fifteen thousand men for that service. General Clinton did, indeed, anchor at the New York Narrows, just when General Charles Lee reached that city for its defence, but did not risk a landing, and sailed for South Carolina, only to be repulsed.
The British Crown had no alternative but to seek foreign aid. The appeal to Catharine of Russia for twenty thousand men was met by the laconic response, "There are other ways of settling this dispute than by resort to arms." The Duke of Richmond prophetically declared, "The colonies themselves, after our example, will apply to strangers for assistance." The opposition to hiring foreign troops was so intense, that, for many weeks, there was no practical advance in preparations for a really effective blow at the rebels, while the rebellion itself was daily gaining head and spirit.
The British army, just before the battle of Long Island, including Hessians, Brunswickers, and Waldeckers, was but a little larger than that which the American Congress, as early as October 4, 1775, had officially assigned to the siege operations before Boston. That force was fixed at twenty-three thousand, three hundred and seventy-two men. General Howe landed about twenty thousand men. With the sick, the reserves on Staten Island, all officers and supernumeraries included, his entire force exhibited a paper strength of thirty-one thousand, six hundred and twenty-five men. It is true that General Howe claimed, after the battle of Long Island, that his entire force (Hessians included) was only twenty four thousand men, and that Washington opposed the advance of his division with twenty thousand men. The British muster rolls, as exhibited before the British Parliament, accord with the statement already made. The actual force of the American army at Brooklyn was not far from nine thousand men, instead of twenty thousand, and the effective force (New York included) was only about twenty thousand men. As the British regiments brought but six, instead of eight, companies to a battalion, there is evidence that Washington himself occasionally over-estimated the British force proper; but the foreign battalions realized their full force, and they were paid accordingly, upon their muster rolls. Nearly three fifths of General Howe's army was made up from continental mercenaries. These troops arrived in detachments, to supplement the army which otherwise would have been entirely unequal to the conquest of New York, if the city were fairly defended.
If, on the other hand, Washington had secured the force which he demanded from Congress, namely, fifty-eight thousand men, which was, indeed (but too tardily), authorized, he could have met General Howe upon terms of numerical equality, backed by breast-works, and have held New York with an equal force.
This estimate, by Washington himself, of the contingencies of the campaign, will have the greater significance when reference is made to the details of British preparations in England.
While Congress did, indeed, as early as June, assign thirteen thousand additional troops for the defence of New York, the peremptory detachment of ten battalions to Canada, in addition to previous details, persistently foiled every preparation to meet Howe with an adequate force. Regiments from Connecticut and from other colonies reported with a strength of only three hundred and sixty men. While the "paper strength" of the army was far beyond its effective force, even the "paper strength" was but one half of the force which the Commander-in-chief had the right to assume as at his disposal.
Other facts fall in line just here.
At no later period of the war did either commander have under his immediate control so large a nominal force as then. During but one year of the succeeding struggle did the entire British army, from Halifax to the West Indies inclusive (including foreign and provincial auxiliaries), exceed, by more than seven thousand men, the force which occupied both sides of the New York Narrows in 1776. The British Army at that time, without its foreign contingent, would have been as inferior to the force which had been ordered by Congress (and should have been available) as the depleted American army of 1781 would have been inferior to the British without the French contingent.
The largest continental force under arms, in any one year of the war, did not greatly exceed forty thousand men, and the largest British force, as late as 1781, including all arrivals, numbered, all told, but forty-two thousand and seventy-five men.