Abstract: A combination tool for breakdown of oilwell drill strings which may contain obstructions, corrosive fluids, and trapped, high-pressure gases is disclosed. The tool provides an upper rotary hydraulic power wrench or tong, an intermediate, hydraulically operated pressure chamber for enclosing the drill string joint during the breakdown process, and a lower backup tong for securing a section of the drill string against the rotary effort of the upper tong. The combination is mounted on a drill platform to be rolled from a position free of the drill string and rotary table to a position over the rotary table encompassing a joint in the drill string to be broken down. Chicksan lines connect the pressure chamber of the tool to a support base permitting the controlled bleedoff of trapped pressure.