Cruiser rules

Cruiser rules is a colloquial phrase referring to the conventions regarding the attacking of a merchant ship by an armed vessel. Here cruiser is meant in its original meaning of a ship sent on an independent mission such as commerce raiding. A cruiser in modern naval terminology refers to a type of ship rather than its mission. Cruiser rules govern when it is permissible to open fire on an unarmed ship and the treatment of the crews of captured vessels. During both world wars, the question was raised of whether or not submarines were subject to cruiser rules. Initially, submarines attempted to obey them, but abandoned them as the war progressed. The essence of cruiser rules is that an unarmed vessel should not be attacked without warning. It can be fired on only if it repeatedly fails to stop when ordered to do so or resists being boarded by the attacking ship. The armed ship may only intend to search for contraband (such as war materials) when stopping a merchantman. If so, the ship may be allowed on its way, as it must be if it is flying the flag of a non-belligerent, after removal of any contraband. However, if it is intended to take the captured ship as a prize of war, or to destroy it, then adequate steps must be taken to ensure the safety of the crew. This would usually mean taking the crew on board and transporting them to a safe port. It is not usually acceptable to leave the crew in lifeboats. This can only be done if they can be expected to reach safety by themselves and have sufficient supplies and navigational equipment to do so. The cruiser rules evolved during the 17th century when the issuing of letters of marque to privateers was at its peak. They were initially an understanding of the honourable way to behave rather than formal international agreements. A formal agreement between Great Britain and France at the end of the Crimean War was extended internationally at the Paris Declaration Respecting Maritime Law in 1856. It was signed by all maritime nations except the United States and Spain.