Emanuel Lasker, the second chess world champion, was a very interesting person. I read here that “During World War I, Lasker […] invested all of his money in German war bonds. At the end of the war, he had lost all his money and savings. During that period, he wrote a book declaring that Germany had to win the war if civilization were to be saved.” However, I was unable to find any other reference to the existence of such a book. For instance, the German Wikipedia article about Lasker mentions no book published by him during the war and the first book he published after the war (Die Philosophie des Unvollendbar, Leipzig 1919) seems to be a book about Philosophy. So, was such book ever written?
It's likely not a book per se, but a brochure, of which he published several during the war.
The most likely candidate would be the pamphlet "Die Selbsttäuschung unserer Feinde", Berlin, 1916. (On the self delusions of our enemies)
Sadly, the Emanuel Lasker Gesellschaft should have this, but their site is currently "under construction".
Nota bene he was by far not unique among German intellectuals to pit (German) culture against (Western) civilization. More about this in Making Sense of the War (Germany).
That pamphlet seems to be quite rare now. If you are really dedicated to read the original, a few libraries still have it.