If a contract which is entered into before the outbreak of war involves continued commercial intercourse between those who become alien enemies to one another by reason of the outbreak of the war, the outbreak of the war ordinarily terminates such contract,1 whether such contract is entered into between citizens of the different belligerent powers,2 or whether it is entered into between citizens of one of the belligerent powers who are domiciled therein, and who attempt to enforce such contract in its courts.3