In explaining his plan to the Cabinet, Armstrong pointed out that the attack from Lake Champlain on Montreal could not begin before May 1; that Kingston, between April 1 and May 15, was shut from support by ice; that not more than two thousand men could be gathered to defend it; and that by beginning the campaign against Kingston rather than against Montreal, six weeks’ time would be gained before reinforcements could arrive from England.[157] Whatever defects the plan might have, Kingston, and Kingston alone, possessed so much military importance as warranted the movement. Evidently Armstrong had in mind no result short of the capture of Kingston. Dearborn received these instructions at Albany, and replied, February 18, that nothing should be omitted on his part in endeavoring to carry into effect the expedition proposed.[158] Orders were given for concentrating the intended force at Sackett’s Harbor. During the month of March the preparations were stimulated by a panic due to the appearance of Sir George Prevost at Prescott and Kingston. Dearborn hurried to Sackett’s Harbor in person, under the belief that the governor-general was about to attack it. Armstrong estimated the British force at Kingston as nine hundred regulars, or two thousand men all told; and his estimate was probably correct. The usual garrison at Kingston and Prescott was about eight hundred rank-and-file. In both the British and American services, the returns of rank-and-file were the ordinary gauge of numerical force. Rank-and-file included corporals, but not sergeants or commissioned officers; and an allowance of at least ten sergeants and officers was always to be made for every hundred rank-and-file, in order to estimate the true numerical strength of an army or garrison. Unless otherwise mentioned, the return excluded also the sick and disabled. The relative force of every army was given in effectives, or rank-and-file actually present for duty. In the distribution of British forces in Canada for 1812–1813, the garrison at Prescott was allowed three hundred and seventy-six rank-and-file, with fifty-two officers including sergeants. To Kingston three hundred and eighty-four rank-and-file were allotted, with sixty officers including sergeants. To Montreal and the positions between Prescott and the St. John’s River about five thousand rank-and-file were allotted.[159] At Prescott and Kingston, besides the regular troops, the men employed in ship-building or other labor, the sailors, and the local militia were to be reckoned as part of the garrison, and Armstrong included them all in his estimate of two thousand men. The British force should have been known to Dearborn nearly as well as his own. No considerable movement of troops between Lower and Upper Canada could occur without his knowledge. Yet Dearborn wrote to Armstrong, March 9, 1813, from Sackett’s Harbor,[160]--