A series of international crises strained the League to its limits, the earliest being the invasion of Manchuria by Japan and the Abyssinian crisis of 1935/36 in which Italy invaded Abyssinia, one of the only free African nations at that time. The League tried to enforce economic sanctions upon Italy, but to no avail. The incident highlighted French and British weakness, exemplified by their reluctance to alienate Italy and lose her as their ally. The limited actions taken by the Western powers pushed Mussolini's Italy towards alliance with Hitler's Germany anyway. The Abyssinian war showed Hitler how weak the League was and encouraged the remilitarization of the Rhineland in flagrant disregard of the Treaty of Versailles. This was the first in a series of provocative acts culminating in the invasion of Poland in September 1939 and the beginning of the Second World War.

Who was first to invade Manchuria?