In The Nature and Origins of Japanese Imperialism, Donald Calman traces Japan's twentieth-century imperialism back to the economic imperatives at the root of the country's 1873 crisis. Calman shows that the prospect of economic gain through overseas expansion was the central issue of that year's political struggles. He goes on to demonstrate that Japan had a long, earlier tradition of aiming for economic expansion overseas and that much of the writing on Japan has played down the true extent of Japanese imperialism.