[1] On 20 February, a flying boat from Yokohama Air Group spotted a US carrier task force centered around Lexington 460 nautical miles from Rabaul.

4th Air Group medium bombers were ordered to attack the task force with bombs, since Type 91 aerial torpedoes had not yet arrived at the newly captured outpost at Rabaul.

To make matters worse, external fuel tanks for Mitsubishi A6M Zero fighters stationed at Rabaul had not yet arrived either, which meant that they could not escort the bombers at such distances.

The attack formation consisted of 17 G4M, each equipped with two 250 kg bombs, and was led by the unit's Hikōtaichō Lieutenant Commander Takuzō Itō, who flew as an observer in the lead aircraft.

[1][3] On 7 August 1942, the 4th Air Group prepared to strike a newly discovered enemy airfield near Milne Bay on New Guinea, when the shocking news of the Allied landing on Guadalcanal came in.