On May 19th, Yeo transferred his operations to Sacketts Harbour, where he began a strict blockade, much to the discomfiture of Chauncey, who still lacked important material for the completion of the _Superior_. It was while attempting to capture several small boats with a part of this material that two British gunboats, three cutters, and a gig, carrying several heavy guns and one hundred and eighty men, started up Sandy Creek on the thirtieth, and ran into an ambush laid by Major Appling and one hundred and twenty American riflemen. In the terrific volleys that followed, the British suffered heavily, eighteen of their number being almost immediately killed and fifty wounded. The entire force was captured with a loss on the American side of but one wounded. On June 6th, Commodore Yeo raised his blockade and from then until July 31st, when Chauncey brought out his squadron, nothing of importance was accomplished with the exception of two or three successful cutting-out expeditions on the part of the Americans. Even after this date, until the close of navigation, the two fleets acted merely in the capacity of watch-dogs, neither daring to attack the other. During the greater part of this period, Yeo was penned up in Kingston, while Chauncey, whose superior force would have made his co-operation of tremendous value to the land forces under General Brown, peremptorily refused this assistance, saying that his object was the destruction of the enemy’s fleet and not to “become a subordinate or appendage of the army.” On the other hand, he could not get Yeo to fight, so that his powerful force remained practically useless. Meanwhile General Brown undertook his contemplated invasion of Canada, sending Generals Scott and Ripley to the attack of Fort Erie, which soon surrendered. A few days later, on July 5th, General Riall with a force of nearly 2000 British met the Americans near Chippewa, and one of the fiercest and most important battles of the war was the result. Notwithstanding the superior numbers of the enemy, the victory fell to the Americans, whose loss was 61 killed and 255 wounded as against 236 killed and 322 wounded on the British side. It was at this critical moment, when a successful and complete invasion of Canada might have been made, that General Brown wrote to Chauncey asking for his co-operation. Soon after this, General Riall was reinforced by 800 men under Sir George Gordon Drummond, and on the 25th of July, General Scott was sent against them with a force of 1200 men.