Additional Protocol I (AP I) to the Geneva Conventions was adopted in 1977 and applies to international armed conflicts, including wars between nations. It significantly expanded protections for civilians and codified principles such as distinction (separating civilians from combatants), proportionality (balancing military advantage against civilian harm), and precaution (taking steps to minimize civilian casualties). Article 54 specifically prohibits attacking objects indispensable to civilian survival, including food supplies, agricultural areas, and drinking water installations. The United States has signed but not ratified AP I, but most of its rules are considered binding customary international law.