means that the gun recoils backward in its cradle, retarded and stopped by hydraulic buffers. It is returned to battery, or the firing position, by either helical springs or by air in a pneumatic recuperator cylinder that is compressed by the force of recoil. This is the most common method used for lighter railway guns and for virtually all field artillery designed after the French introduced their Canon de 75 modèle 1897. Top-carriage recoil is the situation in which the gun is mounted in an upper carriage that moves on wheels on fixed rails mounted on the lower. The gun and upper carriage recoil together, restrained by the usual hydraulic buffers. Return to battery is effected either by gravity, through the use of inclined rails, which the gun and carriage have run up, by springs, or even by rubber bands, on some improvised mounts. It is not well-suited to firing at steep upward angles because it cannot absorb much of the vertical component of the recoil force. Sliding recoil has the car body sitting on a set of wooden crossbeams or "sleepers" placed underneath it which have been jacked down on to a special set of girders incorporated into the track so that about half the weight of the mount has been transferred to them from the trucks. The gun, car body and trucks all recoil together with the friction generated by the crossbeams sliding on the girders absorbing the recoil force after moving only about to the rear. The sleepers must be jacked up again to allow the gun to roll forward to its firing position. This was often done by handwheels driving gear trains attached to the wheels, or even by electric motors on more modern mounts. Almost all of these type of mounts were of the non-traversing type and had to be fired from a curved section of track or turntable. The American post–World War I assessment of railway artillery praised its ruggedness, ease of manufacture and convenience in service, but acknowledged its unsuitability for smaller guns, due to excessive time of operation and lack of traverse, and that it was not suitable for the largest howitzers firing at high angles because of the enormous trunnion forces. With rolling recoil the entire gun, mount, and carriage rolls backward, typically between , restrained only by the brakes. The mount was winched back into firing position by cables fastened