A US reconnaissance flight over Truk prompts Admiral Koga to pull the Combined Fleet back, mostly to Palau.

What happened

Truk Lagoon had been the Combined Fleet’s preferred anchorage for the first two years of the Pacific War. When a US reconnaissance plane flew over, Admiral Koga ordered the fleet out, and within days most of it had moved west to Palau.

Why it matters

Because the fleet left, the US raid two weeks later caught mainly cruisers, destroyers and transport ships.