I've followed the talk about the movie and got interested where the phrase came from. BTW these guys got their buts kicked during the Battle of New Orleans. It is still impressive history:
"The Thin Red Line"
Balaklava
1854

    After New Orleans the 93rd spent 10 years in Britain and Ireland, 11 years in the West Indies, and a further 13 at home and in Canada.
    In 1854 they went to the Crimea, took part in the storming of the heights above the Alma and then moved on to Sevastopol.
    They were led by Sir Colin Campbell who was so pleased with them at Alma that he had obtained Lord Raglan's permission to wear a Highland bonnet instead of his general's cocked hat for the rest of the campaign.
    On the 24th October they routed the Russian Cavalry charge at Balaklava earning themselves the nickname of "The Thin Red Line". In the museum a diorama with commentary explains the details of the battle.
    The Russian force was 25,000 strong; but only their massed cavalry pushed right forward down the road to Balaklava. Part of this threat was parried by the immortal charge of Scarlett's Heavy Cavalry Brigade. The rest, a formidable mass, swept on to charge the 93rd drawn up in line, two deep. "There is no retreat from here, men," Campbell told them as he rode down the line, "you must die where you stand." And the reply of John Scott, the right-hand man, was taken up by them all: "Ay, Sir Colin. An needs be, we'll do that." They fired two volleys and the cavalry charge split in half, galloping to right and left and finally into full retreat. Some of the younger soldiers started excitedly forward for a bayonet charge, but Sir Colin called out. "93rd, 93rd, damn all that eagerness!"



    The Times correspondent, W. H. Russell, who standing on the hills above could clearly see that nothing stood between the Russian cavalry and the defenceless British base but the "thin red streak tipped with a line of steel" of the 93rd. Condensed almost immediately into "The Thin Red Line", the phrase has survived to this day as the chosen symbol of everything for which The Argyll and Sutherland Highlanders believe themselves to stand. Asked why he had been so unorthodox as to receive a cavalry charge in line instead of in a square. Sir Colin Campbell said; "I knew the 93rd, and I did not think it worth the trouble of forming a square."