Over a multi-frame event, I would suppose that each frame could have different objectives. Japanese objectives could be successfully bombing Port Moresby (this was still going on, the last major bombing raid took place on April 12th 1943), driving the allies out of and capturing Wau airstrip, and successfully delivering troops and supplies to Lae (aka ships survive the Battle of Bismark Sea).
The allies could be on the defensive in frame 1 (defend Port Moresby), frame 2 could be hold Wau and deliver reinforcements (P-39's were escorting C-47's on a regular basis, bringing fresh Australian troops to Wau), and Frame 3 would culminate in the Battle of Bismark Sea.