Some believed at the time that Spruance missed a significant opportunity to sink even more ships and should have pursued the "defeated" enemy fleet. In fact, Yamamoto was bringing forward his battleships and cruisers in hopes of a decisive night engagement against Spruance's carriers. Two years later during the Battle of the Philippine Sea, when covering USN landings on Saipan in the Mariana Islands, Spruance's carrier aircraft and submarines sank three IJN carriers and virtually wiped out the Japanese naval aircraft capability for the rest of the war. Again some believed Spruance should have followed up immediately by pursuing the defeated and retreating enemy fleet, then comprising 90% of IJN's naval forces. Again, however, Spruance chose to defend the Allied landings at Saipan, which he perceived as his principal assignment from Nimitz, rather than to attempt to sink more ships.