Mid-September the Army decided to officially form a CWS "Flame Thrower Group" with Col Unmacht requesting 56 additional Seabees. The group included more Army CWS and 81st Ordnance men as well. It was apparent that a larger flamethrower on a bigger tank would be more desirable, but very few tanks were available for conversion. Operation Detachment was next and Col Unmacht's group located eight M4A3 Sherman medium tanks for it. The Seabees worked to combine the best elements from three different flame units: the Ronson, the Navy model I and those Navy Mk-1s the Navy gave up. MMS1c A.A. Reiche and EM2c Joseph Kissel are credited with designing the CB-H1. Installation required 150 lbs of welding rod, 1100 electrical connections, and cost between $20,000-25,000 per tank(adj. for inflation $288,000-$360,000 in 2019). The CB-H1 flamethrower operated on 300 psi which gave it a range of and could transverse 270°. This model was quickly superseded by the CB-H2 that was far better. EM2c Kissel and SF1c J.T. Patterson accompanied the tanks to oversee maintenance during the battle of Iwo Jima. Kissel filled in as an assistant driver/gunner with tank crews on 20 days of the operation.