Complex sentence: At sea, the great Battle of the Three Navies between the U.S.A. on one side, and the United Kingdom and Japan on the other, prevents the "Entente" from recapturing the Sandwich Islands (Hawaii).
Split into simpler sentences: At sea, the great Battle of the Three Navies is fought, with the U.S.A. on one side and the United Kingdom and Japan on the other. This prevents the "Entente" from recapturing the Sandwich Islands (Hawaii).