The first modification to Sherman tanks involved the installation of the small E4-5 mechanized flame thrower in place of the bow machine gun. This was only a marginal improvement; the system’s short range, modest fuel supply, and awkward aiming process hardly offset the loss of the machine gun. Even so, each of the three tank battalions employed E4-5-equipped Shermans during Iwo Jima. The best solution to marrying effective flame projection with mechanized mobility resulted from an unlikely inter-service task force of Seabees, Army Chemical Warfare Service technicians, and Fleet Marine Force tankers in Hawaii before the invasion. According to Lieutenant Colonel William R. Collins, commanding the 5th Tank Battalion, this inspired group of field-expedient tinkerers modified the Mark I flame thrower to operate from within the Sherman’s turret, replacing the 75mm main gun with a look-alike launch tube. The modified system could thus be trained and pointed like any conventional turret gun. Using napalm-thickened fuel, the “Zippo Tanks” could spew flame up to 150 yards for a duration of 55-80 seconds, both quantum tactical improvements. Unfortunately, the _ad hoc_ modification team had only sufficient time and components to modify eight M4A3 tanks with the Mark I flame system; four each went to the 4th and 5th Tank Battalions. The 3d Tank Battalion, then staging in Guam, received neither the M4A3 Shermans nor the field modifications in time for Iwo Jima, although a number of their “A2” tanks retained the E4-5 system mounted in the bow. The eight modified Sherman flame tanks proved ideal against Iwo Jima’s rugged caves and concrete fortifications. The Japanese feared this weapon greatly; time and again suicide squads of “human bullets” would assail the flame tanks directly, only to be shot down by covering forces or scorched by the main weapon. Enemy fire and the rough terrain took their toll on the eight flame tanks, but maintenance crews worked around the clock to keep them functional. In the words of Captain Frank C. Caldwell, a company commander in the 26th Marines: “In my view it was the flame tank more than any other supporting arm that won this battle.” Tactical demands for the flame tanks never diminished. Late in the battle, as the 5th Marine Division cornered the last Japanese defenders in “The Gorge,” the 5th Tank Battalion expended napalm-thickened fuel at the rate of 10,000 gallons per day. The division’s final action report stated that the flame tank was “the one weapon that caused the Japs to leave their caves and rock crevices and run.” [Illustration: _A Marine flame tank, also known as a “Ronson,” scorches a Japanese strongpoint. The eight M4A3 Shermans equipped with the Navy Mark I flame-thrower proved to be the most valuable weapons systems on Iwo Jima._ Department of Defense Photo (USMC) 140758 ] ] [Sidebar (page 42): Iwo’s Fire Brigades: The Rocket Detachments