The 2k or so marines sailing toward Iran from the Pacific, leaving two weeks after the war started for some reason, are not numerous enough to take and hold contested land, like Kharg Island, without heavy casualties. They may be able to make a beachhead in the province of Baluchestan where: the land is further away from the Strait of Hormuz, further away from Tehran, the US has better air supremacy, a landing would be surrounded by open lands where an Iranian attack could be easily seen, and the locals may be sympathetic because they are a different ethnic group and religion than the Persians and already have separatist rebels.