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The forces converged in the largest sea battle of World War II up to that point. Over the previous month American destroyers had destroyed 17 of 25 submarines out of Ozawa's screening force. Repeated U.S. raids destroyed the Japanese land-based planes. Ozawa's main attack lacked coordination, with the Japanese planes arriving at their targets in a staggered sequence. Following a directive from Nimitz, the U.S. carriers all had combat information centers, which interpreted the flow of radar data and radioed interception orders to the Hellcats. The result was later dubbed the Great Marianas Turkey Shoot. The few attackers to reach the U.S. fleet encountered massive AA fire with proximity fuzes. Only one American warship was slightly damaged.

How many of Ozawa's submarines were sunk by American destroyers?
17