Merrill's Marauders - the 5307th Composite Unit (provisional) - was a US combat unit that fought in South-East Asia during World War II.
In the course of five months in 1944 they trekked 750 miles through some of the worst jungle terrain in Burma, and fought in five major battle and countless other skirmishes. In addition to combat losses, their forces were diminished by typhus, malaria and dysentery, and further weakened by low supplies - the 2,800-calorie, daily ration packs they were provided would have been sufficient for most other forces, but not men asked to hike, climb and hack their way through the hot, humid, Burmese jungle.
The force, named after their commander, General Frank Merrill, made their name by taking on larger, more heavily armed Japanese forces and beating them, again, and again. They continued on, without reinforcements or rest until, by the time of their last battle, at Myitkyina, only 200 of the original force of 2,750 were present. The Wikipedia entry notes that at the end of this final battle only two "had never been hospitalized with wounds or major illness."
Merrill's Marauders is a mostly accurate account of this fighting force, and how they were asked to battle on, beyond endurance. This is a good story and great film for anyone interested in World War II. The reason I gave it only a 6 out of 10 is because the many battle scenes in the film are, by today's standards, quite unrealistic: we see almost no gore, with enemy soldiers simply falling down when shot. So anyone who has seen Saving Private Ryan or some other modern, ultra-realistic war film, will find it hard to take these battles seriously. But this lack of gore is also a selling feature. It means this film is appropriate for a much younger audience - fathers could watch this with their sons, to show them a piece of history. That said, the battles do still involve explosions, lots of shooting, and of course, soldiers dying, so they will still be too intense for the very young.
One other caution - while the language in here is pretty clean - no one takes God's name in vain - there is one or two uses of "damn" and "hell."