The Second Reich and World War 1
In 1862 Bismarck began a process which, by 1871, had unified Germany under Emperor William I; this Second Reich lasted until the aftermath of the Great War.
This is a basic, but very clear, colour map depicting both the political makeup of the German Empire, and its borders. The key, and annotation, is in English.
This slightly simplistic look at the Unification of Germany is supported by five scanned stamps.
This is a short, but analytical, biography of Kaiser Wilhelm II, which introduces both his life, and some of the surrounding historical debates.