Brown might have been greatly strengthened at Niagara by drawing from Detroit the men that could be spared there; but the Cabinet obliged Armstrong to send the Detroit force--about nine hundred in number--against Mackinaw. Early in July the Mackinaw expedition, commanded by Lieutenant-Colonel Croghan, started from Detroit, and August 4 it was defeated and returned. Croghan’s expedition did not even arrive in time to prevent a British expedition from Mackinaw crossing Wisconsin and capturing, July 19, the distant American post at Prairie du Chien.[42] Armstrong did not favor Croghan’s expedition, wishing to bring him and his two batteries to reinforce Brown, but yielded to the Secretary of the Navy, who wished to capture Mackinaw,[43] and to the promises of Commodore Chauncey that on or before July 1 he would sail from Sackett’s Harbor, and command the Lake. In reliance on Chauncey, the Cabinet, except Monroe, decided that Major-General Brown should cross to the Canadian side, above the Falls of Niagara, and march, with Chauncey’s support, to Burlington Heights and to York.[44] This decision was made June 7, and Armstrong wrote to Brown, June 10, describing the movement intended.[45] The Secretary of the Navy, he said, thought Chauncey could not be ready before July 15: “To give, however, immediate occupation to your troops, and to prevent their blood from stagnating, why not take Fort Erie and its garrison, stated at three or four hundred men? Land between Point Abino and Erie in the night; assail the Fort by land and water; push forward a corps to seize the bridge at Chippawa; and be governed by circumstances in either stopping there or going farther. Boats may follow and feed you. If the enemy concentrates his whole force on this line, as I think he will, it will not exceed two thousand men.” Brown had left Sackett’s Harbor, and was at Buffalo when these orders reached him. He took immediate measures to carry them out. Besides his regular force, he called for volunteers to be commanded by Peter B. Porter; and he wrote to Chauncey, June 21,[46] an irritating letter, complaining of having received not a line from him, and giving a sort of challenge to the navy to meet the army before Fort George, by July 10. The letter showed that opinion in the army ran against the navy, and particularly against Chauncey, whom Brown evidently regarded as a sort of naval Wilkinson. In truth, Brown could depend neither upon Chauncey nor upon volunteers. The whole force he could collect was hardly enough to cross the river, and little exceeded the three thousand men on whose presence at once in the boats Alexander Smyth had insisted eighteen months before, in order to capture Fort Erie.