This clearly written Understanding treatise is designed to explain what international law is, why it exists, and the basic subjects it covers. The law of treaties is given particular attention, chiefly because of the increasing importance of the treaty in international life. The number of treaties has mushroomed since the Second World War and many of these agreements include over 100 states as parties. Because of their number and the breadth of their coverage, treaties are thus the main form of international legislation.