Reach was the the prequel installment of the Halo franchise that charts the beginning of the Human/Covenant war. And if the militia members you're escorting in the mission 'Nightfall' represent the collective intelligence of the population on Reach, it's no wonder the Covenant took the planet. Even the word militia evokes the image of doomsday preppers canning their own urine for when the government comes to take their guns and jerky dehydrators.
No wonder the covenant made short work of them. Properly trained military personal should be the only ones handling rocket launchers. This is something that really shouldn't have to be said out loud. Please don't touch the rocket launchers. Talking to you. In the back. With the lazy eye. You encounter the militia members as they're dragging found/stolen UNSC armaments from a river and they decide to do what they can to 'help' you and your team infiltrate a Covenant Pylon site. The rebels define 'help' as blowing themselves up the second they manage to get their hands on a rocket launcher. They're also happy to stand directly under Covenant drop ships and charge Elites and Hunters solo. A word of warning: they will all be killed at the beginning of this mission, and like most ecortees you're happy to see them go.