In addition to international law, the laws and military codes of all nations protect hospitals and medical personnel. This has been a basic part of international law since it was started in 1864. It is also a part of four Geneva Conventions of 1949 and was added to in 1977. Doctors, nurses and medical personnel have a duty to treat the sick and wounded in a war zone. Attacking them or the hospitals they work in is a crime on many levels.