Reconnaissance flights from Japanese submarines in December, January and February using Yokosuka E14Y1 (Glen) seaplanes revealed the speed with which the Americans were recovering from the attack on Pearl Harbor of 7 December 1941. A wildly optimistic plan was conceived to bomb the harbor a second time. However, no aircraft carriers were in range or available, so the new Kawanishi H8K1 (Emily) was given its first operational task. There were only two of these large seaplanes to be had, but nonetheless they set off from Wotje Atoll in the Marshalls with four 250 kilogram bombs each to make the 4,000-mile round trip to Oahu. They refueled from submarines at French Frigate Shoals, setting down at sunset on 3 March and taking off for Pearl Harbor at 2138. American espionage was better by now and they were reading code JN-25 so Commander Joseph Rochefort was able to inform Lieutenant Commander Edwin T. Layton (Layton, Edwin T.) of a possible attack. The incoming aircraft were detected by radar on Kauai Island early on 4 March and four P-40s were sent up to investigate as well as five PBY Catalinas to look for support ships. Both Emilys dropped their bombs, one probably in the sea and the other about five miles east of the target, and both survived the mission. The American defense arrangements had again been exposed as ineffective. Layton appreciated the truth and sent patrol ships to occupy French Frigate Shoals. When, in preparation for the Battle of Midway (Midway, Battle of), the Japanese again tried to establish a forward refueling post there the Americans were present and the submarine withdrew, conceding the position from which the Japanese might have been able to conduct crucial reconnaissance and thus avoid defeat.