Gilbert Islands; Wikimedia Commons
On the same day as the attack on Pearl Harbor, Japan invaded the Gilbert Islands, occupying them by December 10, 1941.
One of these islands would become infamous. In the November 1943 Battle of Tarawa, the ~12,000 man U.S. Marine 2nd Division suffered 894 killed and 2188 wounded, while 4,690 of 4,836 Japanese and Korean defenders of the island were killed.