In late August, two U-boats made a joint raid on the St. Lawrence. sank nine ships and damaged another in a two-week period, escaping attacks by escort vessels each time and sinking the Flower-class corvette on 11 September. was less successful in attacking merchant shipping but it sank the armed yacht and heavily damaged . Eastern Air Command positioned itself to better defend the remaining convoys by establishing a "Special Submarine Hunting Detachment" of No. 113 Squadron RCAF in Chatham, New Brunswick. They made their first U-boat attack on 9 September, when Pilot Officer R.S. Keetley dove on "U-165", about south of Anticosti Island. He did not do much damage to the submarine, but subsequent naval and air activity in the area frustrated the U-boat's efforts to attack other convoys. The RCN requested additional forces from Western Local Escort Force, receiving two old Royal Navy destroyers with improved radar to combat the U-boat threat.