Last week, U.S. military officials accused Iran of arming Iraqi insurgents with bombs, missiles, and rockets for attacks on American troops. Apparently, serial numbers and markings on seized munitions indicate they came from Iran. (Click here for a PDF of the U.S. military intelligence report.) Why do bombs need serial numbers?
For inventory and quality control. When a bullet, explosive, or any kind of ammunition is manufactured, it may be marked with a unique serial number and the date of manufacture. (A bomb may also include information indicating which factory produced it.) This information simplifies the process of tracking missing or damaged munitions. For example, if a bullet misfires, the military can use its markings to identify and scrap the entire lot it came from. The date of manufacture is important because the components in ammunition begin to degrade and become unreliable after about 15 years.
Military intelligence analysts have to learn to identify the manufacturer markings and serial numbers of each country's munitions, since there are no international guidelines for labeling. The exact markings on grenades, bombs, and bullets will vary depending on the country and sometimes on the specific company that does the manufacturing.
Why does the Iranian TNT have markings in Farsi, while the other rounds seem to be labeled in English? Since Iran sells munitions on the international market, it makes more sense to use a language that is spoken far and wide. (You don't have to use English, though; China and Russia sell arms marked with Chinese and Cyrillic characters.) In recent years, U.S. manufacturers have begun to augment their markings with bar codes that can be tracked by computer.
Surveying the serial numbers on bullets and projectiles can be an effective way to measure the flow of arms into conflict zones. Last year, Oxfam reported that bullets manufactured in the United States, Greece, Russia, and China had ended up in the Democratic Republic of Congo, in spite of a U.N. arms embargo. Last summer, Israel examined the serial numbers on rockets fired by Hezbollah and concluded they came from Russia by way of Syria. * Serial numbers are also used by national and international police to track down illegal sales of ammunition. Meanwhile, the United Nations is now attempting to create an international standard for the tracing and marking of ammunition.
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Explainer thanks: Guy Ben-Ari of the Center for Strategic and International Studies, Philip Coyle of the Center for Defense Information, Pablo Dreyfus of Viva Rio, Colby Goodman of Amnesty International USA, and John Pike of GlobalSecurity.org.