I've looked at multiple posts on the subject, and everyone says the same thing: "They are similar but have different missions." Honestly in today's military, is there really a difference in the missions of the two branches Infantry-wise? It seems like in Afghanistan, both branches patrol, set up COPs, and support the Afghans. How does this make their missions any different in the 21st century? I realize the Marines were created for maritime and amphibious warfare, but would the Marines really be the first to land in a modern day conflict?