Though both the French and the Germans had for a number of years been experimenting with armoured cars of various patterns, the Belgians, who had never before given the subject serious consideration, were the first to evolve and to send into action a really practical vehicle of this description. The earlier armoured cars used by the Belgians were built at the great Minerva factory in Antwerp and consisted of a circular turret, high enough so that only the head and shoulders of the man operating the machine-gun were exposed, covered with half-inch steel plates and mounted on an ordinary chassis. After the disastrous affair near Herenthals, in which Prince Henri de Ligne was mortally wounded while engaged in a raid into the German lines for the purpose of blowing up bridges, it was seen that the crew of the auto-mitrailleuses, as the armoured cars were called, was insufficiently protected, and, to remedy this, a movable steel dome, with an opening for the muzzle of the machine-gun, was superimposed on the turret. These grim vehicles, which jeered at bullets, and were proof even against shrapnel, quickly became a nightmare to the Germans. Driven by the most reckless racing drivers in Belgium, manned by crews of dare-devil youngsters, and armed with machine-guns which poured out lead at the rate of a thousand shots a minute, these wheeled fortresses would tear at will into the German lines, cut up an outpost or wipe out a cavalry patrol, dynamite a bridge or a tunnel or a culvert, and be back in the Belgian lines again almost before the enemy realized what had happened.