By the late 1890s, breech-loading rifled guns had replaced smooth-bore muzzle loaders; otherwise, field artillery operated much as it had for the past several centuries. The charge of black gunpowder and the projectile were loaded separately. The crew aimed (“laid”) the gun, then stood well back from the piece. A soldier pulled a lanyard, firing the gun and producing a cloud of white smoke that immediately obscured the gunners’ view of the enemy and revealed the gun’s own position. The carriage, on which the barrel was hard-mounted, lurched backward several feet. The gunners ran back to the gun, wheeled it by hand into its (approximate) starting position, and aimed it again, to the extent that they could see anything. The rate of fire was thus limited by the time it took to stand clear of the recoil, reposition the gun, and re-lay it. A typical firing cycle took 15 seconds. Constantly repositioning the gun quickly wore out the crews.
In 1896 two French artillery captains invented a hydraulic shock absorber that took up the recoil of the barrel and returned the tube to its firing position, eliminating the motion of the carriage. Self-contained ammunition combined smokeless powder and a projectile within a single brass casing. Improved devices for aiming and fuze-setting were developed. These features became the basis for the 75 mm gun, which the French adopted in 1897. Gunners could now fire as fast as they could load – twenty to thirty rounds per minute – with no need to re-lay the gun once the shells were hitting their target. Equally important, forward observers could now give target coordinates to the gunners, enabling the latter to fire accurately from concealed positions at targets they could not see.
A 75-mm gun crew in action was a wonder to observe. The designers had thought hard about arranging the gun’s controls for ease and speed of use. A rotating breech mechanism could be closed and opened with the throw of a single lever; this replaced the usual door-like hatch that had to be shut and then latched down. The shell weighed only 12 pounds and, because it combined the charge and projectile in a single package, could easily be loaded by one man. The natural frequency of the gun’s firing cycle exactly matched the loading and firing cadence of the crew, achieving a near-perfect integration of man and machine; neither had to stop to wait for the other at any point in the operation.
The gun in action. Source: YouTube
A firing cycle started with the gun barrel in its farthest-back position. The loader, standing to the left rear of the gun, shoved a shell into the open breech. As the barrel, propelled forward by the gun’s hydraulic mechanism, reached the firing position, the breech-worker, at the right rear of the gun, closed the breech by pushing its handle downward. At the same time the gun-layer, stationed to the left of the tube, checked the barrel’s aim and, at the top of its travel, gave the signal to fire. (The French used two gun-layers, one for azimuth and one for elevation; the Americans used a single man for both.) The breech-worker yanked the firing lanyard, the shell sped on its way, and the barrel – but not the gun carriage – jerked backward. As the hydraulic cylinder slowed the tube’s recoil, the breech-worker opened the breech by hauling up on the lever, automatically ejecting the spent shell casing. As he did this the loader pivoted to his left and the assistant loader handed him a fresh shell from the caisson. The loader pivoted right, rammed the new shell into the open breech, and the cycle began again. A well-trained crew could perform this lethal ballet in two to three seconds and keep it up for hours. (One can observe this action in films taken by French and American cameramen; see, for example, CBS News, World War I: The Complete Story, 2008, Volume III, “The Tide Turns,” 0:03:25 (DVD).)
The gun had its drawbacks – it fired in a flat trajectory, so it could not reach into trenches or dugouts, and its shells were too light to penetrate fortifications or deep shelters. (Heavy guns and howitzers were developed for those purposes.) But against troops in the field it was deadly. The “75” is credited, along with the sophisticated French rail system and internal lines of communication, with stopping the German offensive in 1914.
The French kept the 75 well secret until 1901, when they used it in the Boxer Rebellion. Other countries quickly understood its revolutionary implications and developed their own quick-firing models. The British came out with a 76 mm (“13-pounder”) gun and an 83.3 mm (“18-pounder”) in 1904. A year later, Germany added recoil absorption and other improvements to its obsolete 77 mm cannon; even so, the upgraded gun could achieve a rate of fire of only 10 rounds per minute and its recoil mechanism was inferior to that of the French. The United States, after several false starts, could not develop a practical weapon in time for World War I; it obtained all of its field artillery – about 1,800 75s and 1,000 heavier guns – from the French.
As the first rapid-firing artillery piece, the 75 can be credited, along with the machine gun, as being among the first manifestations of modern land warfare.
© 2017 Gene Fax