The inter-war period saw the battleship subjected to strict international limitations to prevent a costly arms race breaking out. Faced with the prospect of a naval arms race against Great Britain and Japan, which would in turn have led to a possible Pacific war, the United States was keen to conclude the Washington Naval Treaty of 1922. This treaty limited the number and size of battleships that each major nation could possess, and required Britain to accept parity with the U.S. and to abandon the British alliance with Japan. The Washington treaty was followed by a series of other naval treaties to limit warship size and numbers, concluding with the Second London Naval Treaty in 1936. These treaties became effectively obsolete on 1 September 1939 at the beginning of Second World War.