Communications, often maligned in earlier amphibious assaults, were never better than at Iwo Jima. Radios and handsets were now waterproof, more frequencies were available, and a variety of radio systems served the varying needs of the landing force. Forward observer teams, for example, used the back-pack SCR-610, while companies and platoons favored the SCR-300 “walkie-talkies,” or the even lighter SCR-536 “Spam Can” portables. Said Lieutenant Colonel James P. Berkeley, executive officer of the 27th Marines and a former communications officer, “At Iwo we had near-perfect communications, all any commander could ask for.” As the battle progressed, the Marines began stringing telephone lines between support units and forward command posts, wisely elevating the wire along upright posts to avoid damage by tracked vehicles. Japanese counterintelligence teams expected to have a field day splicing into the proliferation of U.S. telephone lines, but the Marines baffled them by heavy use of Navajo code talkers. Each division employed about two dozen trained Navajos. The 5th Marine Division command post established six Navajo networks upon arrival on the island. No one, throughout the war, insofar as anyone knew, was ever able to translate the Navajo code talkers’ voice transmissions. [Illustration: _“Iwo Jima,” proof lithograph of two Navajo code talkers, by Sgt John Fabion._ Marine Corps Combat Art Collection ] African-American troops played a significant role in the capture of Iwo Jima. Negro drivers served in the Army DUKW units active throughout the landing. Black Marines of the 8th Ammunition Company and the 36th Depot Company landed on D-day, served as stevedores on those chaotic beaches, and were joined by the 33d and 34th Depot Companies on D+3. These Marines were incorporated into the VAC Shore Party which did Herculean work sustaining the momentum of the American drive northwards. When Japanese counterattacks penetrated to the beach areas, these Marines dropped their cargo, unslung their carbines, and engaged in well-disciplined fire and maneuver, inflicting more casualties than they sustained. Two Marines, Privates James W. Whitlock and James Davis, received the Bronze Star. Said Colonel Leland S. Swindler, commanding the VAC Shore Party, the entire body of black Marines “conducted themselves with marked coolness and courage.”