Some types of modern land mines are designed to self-destruct, or chemically render themselves inert after a period of weeks or months to reduce the likelihood of friendly casualties during the conflict or civilian casualties after the conflict's end. The Amended Protocol II to the Convention on Certain Conventional Weapons (CCW), amended in 1996, requires that anti-personnel land mines deactivate and self-destruct, and sets standards for both. Landmines currently used by the United States military are designed to self-destruct between 4 hours and 15 days depending upon the type. The landmines have a battery and when the battery dies, the landmine self-destructs. The self-destruct system never failed in over 67,000 tested landmines in a variety of conditions. Not all self-destruct mechanisms are absolutely reliable, and most landmines that have been laid throughout history are not equipped to self-destruct. Landmines can also be designed to self-deactivate, for instance by a battery running out of a charge, but deactivation is considered a different mechanism from self-destruction.