Sources show that the M12 Self Propelled Gun was fielded by six battalions from 1942 through 1945 before being disbanded after the war: 174th, 258th*, 557th, 558th, 987th and 991st Field Artillery Battalions. Even though the 558th guns were well worn from action in the European Theater of Operation, the battalion embarked in August 1945 on the USS Breckenridge to the Pacific Theater of Operation in preparation for the invasion of the Japanese home islands. Luckily, Japan surrendered as their ship was heading to the Panama Canal. To the relief of the war weary veterans, the Breckenridge was diverted home to New York City.

*Greg Matthews' research note from 12/28/09: It appears that my search for 258th photos and the M12s will not be successful. Reason, after additional research and information provide by the Col. the historical officer of the 258th, it appears that the 258th was not equipped with the M12s. When the original 258th was federalized its two battalions were split. 1st Battalion remained the 258th and the 2ond battalion became the 991st FA. In 1943 when the M12s were accepted by War department, the 991st got the "new gum", the M12 155mm gpf. The 258th kept the 155mm gpf "Long Toms" towed artillery. Whether the 258th was later equiopped with the M12 is not known or clear at this point.