The remaining planes of Putnam's squadron, along with the other Marines on the island, put up a stout defense but were eventually overwhelmed by superior forces. Putnam, along with Commander Winfield Scott Cunningham, USN and Major James Devereux, USMC, was one of the key leaders of the defense of Wake Island. On December 21, the island was attacked by Japanese aircraft and Putnam took off on an unescorted flight in search of the Japanese aircraft carrier from which the attacking planes were based. For this action, he was awarded the Navy Cross after the war.