Thin Red Line

Etymology
William H. Russell, Times Correspondent at the Battle of Balaclava wrote that he could see nothing between the charging Russians and the British regiment's base of operations at Balaclava but the “thin red streak tipped with a line of steel”. The condensed phrase “the thin red line” came to represent British composure in battle.

Noun

 * 1)  The members the 93rd Regiment of the British Army who met the charge of the Russian cavalry at the  in 1854.
 * 2)  Any thinly spread military unit holding firm against attack.