Sometimes spelt incorrectly by our special relations as 'mechanization'.
Mechanisation is the use of machines, either wholly or in part, to replace and enhance human or animal labour. Unlike automation, which may be devoid of human input, (see Staff Officer) mechanisation requires human participation to provide information and/or instruction.
Red Trousers in Defence Cuts Horror
In military parlance, mechanisation defines an entity that, although primarily mobile by dint of being mounted in dedicated ground vehicles, said vehicles are not entirely or even necessarily tracked or armoured; before 1945, the term used in Britain was either "Lorried" or "Motor". Thus a mechanised Brigade may possess tanks, AIFV's and other tracked/armoured systems, a tangible proportion of the A echelons as well as possibly part of the F echelon will be mounted in vehicles not inherently designed or suitable for a combat environment.
Use of the "M" word around cavalrymen may cause them to wake up and start foaming at the mouth; however, to be fair, the bulk of the inter-war cavalry embraced mechanisation as well as can be expected of an organisation that was being asked to give away what it saw as its most important component, and since that time has managed to successfully combine the "cavalry ethos" with roles in both MBTs and Reconnaissance to the amazement and admiration of all.
As is traditional, having developed the concept to a good start up until 1928, the British then managed to ignore mechanization until almost too late; the Germans however, absorbed the lessons of 1918, and studied the writings of General Sir Hugh Elles, Captain Basil Liddle-Hart, General J.F.C. Fuller, and others. It only remained for strategists like Guderian, and implementers like Rommel, Peiper, Von Luck and Wittman to develop and deploy the concepts back upon the very nation who had initiated them.
It is savagely ironic that the British Army was the only fully mechanised Army in the World in 1939 - the BEF being the most advanced part thereof - and yet a Wehrmacht that made every single one of its infantry Divisions march everywhere and tow guns behind horses managed to defeat it at almost every engagement. The only successful armoured counter attack at Arras was a fortunate accident and was only stopped by Rommel himself rallying the troops at the Divisional gunline. Had the world class equipment been backed up with world class Generalship who knows what might have happened. The lessons learned from the combined arms team that had comprehensively demolished the Germans in 1918 had clearly not been taught since.
The Soviet contribution to the concept of Mechanisation has been largely ignored in the West. A lot of the early work was done in secret with the Wehrmacht. Under the guidance of Marshal Tukhachevsky, the brilliant Civil War commander, and the military theorist Triandafillow the USSR developed the concept of the 'Deep Battle' in the 1920/30s such that by 1932 they had two mechanised Corps. This in turn led to the concept of the 'Deep Operation' which was the forerunner of the stunning Soviet advances of late 1944/45. This doctrine was expressed in the seminal PU-36, or Red Army Regulations 1936. Unfortunately whilst Stalin was extremely wary of his neighbours he feared his own countrymen even more and in the purges of 1937-41 vast numbers of senior officers were purged. This eliminated most who espoused Deep Battle and left the survivors unable to use such concepts for fear of sharing the same fate.
Contrary to popular belief, the German army throughout WWII was primarily non-mechanised, and by 1944, allied forces far outstripped the Germans in both mechanised and armoured formations. I think they did quite well, though, considering?