The division patch worn on Saipan had a gold "4" on a scarlet background, the official colors of the U.S. Marine Corps. The emblem was designed by SSgt John Fabion, a member of the division's Public Affairs Office before the Marshalls Campaign. His commanding officer was astonished to find that when the division attacked Roi Islet in Kwajelein Atoll in the Marshall Islands (January 1944), the layout of the runways on the airstrip there were an exact replica of the "4". The 4th had two Seabee Battalions posted to it during the war. The 121st Naval Construction Battalion was posted to the 20th Marines and redesignated as the 3rd Battalion of the Regiment. They landed with the 4th on Roi-Namur, Saipan and Tinian and received a Presidential Unit Citation for it. The 20th was deactivated and the 121st stayed on Tinian to work on the airfields when the 4th moved on. They were replaced by the 133rd NCB for the assault on Iwo Jima. The 133rd was posted to the 23rd Marines as their shore party until relieved on D plus 18.