Alsace-Lorraine was taken from France in 1871 at the end of the Franco-Prussian War. France got it back after WWI. It may have been largely German-speaking at the time but had been part of France since the reign of Louis XIV and the people considered themselves French.
Screw the French, if Britain and Germany were aligned against France, the world would have been much better off.
Before the rise of Germany, France was “Germany,” the scary power always determined to expand.
I don’t think Britain and Germany should have allied against France, but peace in 1914 depended on Britain and Germany working together and on Russia, Austria-Hungary and Germany cooperating with each other. Some of the failure was Britain’s fault, but Germany and Austria were also foolish and reckless.