Treaties may come to an end in various ways. Most provide for a date of expiration or a time at which notice to terminate must be given if the treaty is not to continue in effect for another specified period. Treaties terminate if one of the signatory states becomes politically extinct or (in the case of political treaties) if the parties are at war with one another. The outbreak of war need not necessarily bring a treaty to an end, however, and provisions compatible with a state of hostilities remain in force, as long as they are not expressly terminated. Treaties relating to the laws of war, of course, remain in effect during hostilities. A treaty may be terminated by mutual consent, and breach of a treaty by one party entitles the other to abrogate it.