Abstract: The invention is an impulse wrench that employs a fluid coupling between its anvil and hammer members. The tool includes a pulse cylinder that forms the tool's hammer and has a shaped inner surface that defines a side wall of a fluid-filled chamber. An end portion of the anvil is received within the chamber and includes two retractable vanes that sweep the pulse cylinder's inner surface when the pulse cylinder is rotating about the anvil. To achieve only a single impact per revolution of the pulse cylinder, fluid bypass channels are employed to intermittently allow fluid to pass around the vanes. In addition, the tool includes a unique torque-sensing shut-off mechanism that is engaged to the tool's motor and makes use of inertia force to actuate a power shut-off device.