WW1 - Camo de mailly - French 400 mm railway howitzer and artillery squadron. The outbreak of the First World War caught the French with a shortage of heavy field artillery. In compensation, large numbers of large static coastal defence guns and naval guns were moved to the front, but these were typically unsuitable for field use and required some kind of mounting. The railway gun provided the obvious solution. By 1916, both sides were deploying railway guns.