With the activation of 4th Marine Division in July 1943 at San Diego, Wensinger was promoted to the rank of colonel and appointed divisional assistant chief of staff for operations and training. After intensive training, he sailed with the division for Pacific area in January 1944 and took part in the Battle of Roi-Namur in the Marshall Islands. The Fourth division under the command of Major General Harry Schmidt captured the large Japanese aerodrome at Roi-Namur and only 51 survivors of an original garrison of 3,500. Wensinger received the Legion of Merit with Combat "V" for the planning of the operation and leadership during the campaign.