In 1920 J.F..C. Fuller Asked: "What had the influence of the tank really been?"

Here's his answer.

The effect of the tank’s mobility on grand tactics was stupendous. Between the winter of 1914 and the summer of 1918, to all intents and purposes, the Allies waged a static war on the Western Front. During these three and a half years various attempts were made to wear down the enemy’s fighting strength as a prelude to a decisive exploitation or pursuit, but these battles of attrition were mutually destructive and the Allies undoubtedly lost more casualties than they inflicted. Attrition without the possibility of surprise  or mobility is a mere “push of pikes,” it is a muscular but brainless operation. At the Third Battle of Ypres it cost us a quarter of a million men. 

Then came the tank, and true attrition was rendered possible; in other words, in tank battles the enemy lost more in human points than we did: it is doubtful whether in killed and wounded we lost, between August 8 and November 11, 1918, as many men as the prisoners we captured. This was only possible by our possessing the means of putting the grand tactical act of penetration into operation, by breaking down the “inviolability” of the German front, and by so doing rendering envelopment a reality.

Tanks Arriving at the Front

In minor tactics it was possible, by means of the tank, to economize life by harmonizing fire and movement and movement and security; the tank soldier could use the whole of his energy in the manipulation of his weapons and none in the effort of moving himself forward; further than this, sufficiently thick armor could be carried to protect him against bullets, shrapnel, and shell splinters. Human legs no longer controlled marches, and human skin no longer was the sole protection to the flesh beneath it. A new direction was obtained, that of the moving firing line; the knight in armor was once again reinstated, his horse now a petrol engine and his lance a machine gun.

Strategy, or the science of making the most of time for warlike ends, had practically ceased since November 1914. Even the great advances of the Germans in 1918 came to an abrupt stop through failure of road capacity, and roads and rails form the network upon which all former strategy was woven. The cross-country tractor, or tank, widened the size of roads to an almost unlimited degree. The earth became a universal vehicle of motion, like the sea, and to those sides which relied on tanks, naval tactics could be superimposed on those of land warfare.

German Prisoners, Canadian Tank, Amiens, August 1918

With the introduction of mechanical movement every principle of war became easy of application and, to-day, to pit an overland mechanical army against one relying on roads, rails, and muscular energy, is to pit a fleet of modern  battleships against one of wind-driven three-deckers. The result of such an action is not even within the possibility of doubt: the latter will for a certainty be destroyed, for the highest form of machinery must win, because it saves time, and time is the controlling factor on the battlefield as in the workshop.

From: TANKS IN THE GREAT WAR, 1914–1918 by Brevet-Colonel J. F. C. FULLER, D.S.O. (Oxfordshire and Buckinghamshire Light Infantry)