Until around 1912, service personnel in most countries were not routinely issued with ID tags. As a result, if someone was killed in action and his body was not recovered until much later, there was little or no chance of identifying the remains. Starting around the time of the First World War, nations began to issue their service personnel with purpose-made ID tags. These were usually made of some form of lightweight metal such as aluminium. However, in the case of the British Army the material chosen was compressed fiber, which was not very durable. Although wearing ID tags proved to be highly beneficial, the problem remained that bodies could be completely destroyed, burned or buried by the type of high explosive munitions routinely used in modern warfare. Additionally, the combat environment itself could increase the likelihood of missing combatants such as jungle warfare, or submarine warfare, and air-crashes in remote mountainous terrain, or at sea. Alternatively, there could be administrative errors e. g. the actual location of a temporary battlefield grave could be misidentified or forgotten due to the "fog of war" Finally, since military forces had no strong incentive to keep detailed records of enemy dead, bodies were frequently buried (sometimes with their ID tags) in temporary graves, the locations of which were often lost or obliterated e. g. the forgotten mass grave at Fromelles. As a result, the remains of missing combatants might not be found for many years, if ever. When missing combatants are recovered and cannot be identified after a thorough forensic examination (including such methods as DNA testing and comparison of dental records) the remains are interred with a tombstone which indicates their unknown status.