Barbed wire

Barbed wire was patented in 1874 by the American Joseph Glidden; as a military obstacle it made its name among other places in the siege of Port Arthur in 1904, where artillery struggled to destroy it. In trench warfare entanglements stood in front of every trench line, in belts several and in places more than ten metres deep. They were laid so as to channel attackers into machine-gun fire, and far enough from the trench that the enemy could not throw grenades into it from the wire. They were put up and repaired at night by parties in no man's land, in time on screw pickets that needed no noisy hammering.

Wire was cheap, easy to repair and resistant to shelling: shells often just tossed it from place to place. Uncut wire stopped many attacks, among them the British one on 1 July 1916 on the Somme. The artillery learned to destroy it, helped by fuzes that burst on contact with the ground, and engineers used wire cutters and elongated explosive charges. Tanks were the most effective at breaking through, crushing the wire under their tracks, as at Cambrai in 1917 and at Amiens in 1918.