Abstract: The invention relates to anti-recoil devices for guns and martars. The anti-recoil device has a brake with a principal cabity which houses a principal piston pierced with holes. The small chamber of the brake is connected by an opening to a subisdiary chamber closed by a fluid-tight piston. The principal cavity and the subsidiary chamber are filled with a liquid whilst a gas under pressure, located on the other side of the fluid-tight piston with respect to the subsidiary chamber, tends to push back the subsidiary piston. A valve partially obturtes the holes of the principal piston, during the return to firing position, in order to brake that return.