High Quality Content by WIKIPEDIA articles! The Battle of the Tenaru, sometimes called the Battle of the Ilu River or the Battle of Alligator Creek, took place August 21, 1942, on the island of Guadalcanal, and was a land battle of the Pacific campaign of World War II, between Imperial Japanese Army and Allied (mainly United States Marine) ground forces. The battle was the first major Japanese land offensive during the Guadalcanal campaign.