Complex sentence: On 26 May, five transports were flying to Wau when they were attacked by 16 Mitsubishi A6M Zeroes, which were engaged by the escorting P-39s of the 35th, 36th and 39th Fighter Squadrons.
Split into simpler sentences: On 26 May, five transports were flying to Wau when they were attacked by 16 Mitsubishi A6M Zeroes. The Zeroes were engaged by the escorting P-39s of the 35th, 36th and 39th Fighter Squadrons.