wwI

The Schneider CA.1 was quite possibly the worst AFV of the whole war. Never mind that it was painfully slow, badly ventilated, cramped and noisy and that it's armour was thin - the same can be said of almost all tanks of the Great War. No, in addition to this, it used a standard Holt Tractor track system, which was way too short for this kind of vehicle, and made all trench-crossing and parapet-climbing very difficult. And its main gun was located in a small embrasure on the right hand side, with a very narrow field of fire as a result - the two MG:s were also mounted in a akward way, that limited their usefulness.
It was first used in combat in an attack outside Barry au Bac, on the Aisne River, on the 16th of April 1917 (a part of Nivelles infamous and futile offensive against Chemin des Dames). The approach to the jumping-off positions was done in broad day-light, in full view of the Forward Observers of the German Artillery, who greeted the slow moving column with showers of shells, inflicting heavy casualties on the AFV:s even before they crossed their own lines. Some tanks managed to breach the German lines, but it was still a disaster. Of the 121 tanks used, 81 were immobilized, 56 of which were destroyed beyond repair.
http://www.patriotfiles.com/forum/showthread.php?t=109724

WW1 was the beginning of a long learning curve where armoured vehicles are concerned. Good post @BravoZulu