friendly-fire
見出に出てくる"friendly fire"に関する調査です。"friendly"には，「友好的な」だけでなく「味方」という意味があります。また，"fire"は「攻撃，（ミサイルや銃弾などの）発射という意味で用いられております。つまり，「同士討ち」（特に銃弾による誤射）という日本語が自然だと思います。
記事によるとこれまでのアフガニスタンでの戦闘で米兵5名，アフガニスタン兵2名が同士討ちで亡くなっているとのことです。主な原因は空からの攻撃による誤射です。空中からは味方かどうかを判別するのが難しいのだと思われます。（Ume）
US investigates five 'friendly-fire' troop deaths
US military officials are investigating the reported friendly-fire incident in southern Afghanistan that killed five American soldiers and two Afghans.
Rear Adm John Kirby said the US had "reason to suspect that friendly fire is the cause here, specifically friendly fire from the air".
Adm Kirby said the Pentagon "would let investigators do their work".
Afghan officials say coalition forces had called for air support to fend off a Taliban ambush in Zabul province.
An Afghan soldier and an interpreter were killed in the incident.
On Tuesday, White House press secretary Josh Earnest said President Barack Obama had been informed of the deaths and that his thoughts and prayers were with the families of those killed.
