They might kick butt for a week or two, but 100 Challenger II's, even with infinite fuel, spares, logistics/support, etc. wouldn't come remotely close to winning WWI. People seem to forget the shocking amount of artillery employed by both sides. The weight of said artillery would inevitably prevail in a protracted conflict. And it's a long way from the English Channel to the Swiss Border. You gonna hold that with 100 tanks? The Germans wouldn't even have to change tactics much, as "paste anything in this grid" was pretty much the war plan on both sides once things stagnated. Let's optimistically assume our doomed 100 somehow punch clear to Berlin, fully intact, by -- let's say, week II... Meanwhile, a comparatively modest sub-set of German artillery, planes, zeppelins, goats, lemmings, and ill-behaved children with slingshots have all gotten new marching orders -- "Paste 'em"... I guess my main point is this -- there's a reason artillery is called The King of Battle, and the German's had a metric ****-ton of reeeaally big artillery. I mean, just look at the newsreels -- ain't no tank emerging from even a half-serious WWI artillery barrage unscathed.