MARSOC is organized into a headquarters, a two battalion Special Operations Regiment, a Foreign Military Training Unit, and a Marine Special Operations Support Group. There are 3-4 Special Operations companies in each battalion. The marines basically lost two of their four Force Recon companies (one of them a reserve unit) in order to build MARSOC. Meanwhile, more troops have been added to division level reconnaissance units, to take up some of that slack. The Special Operations companies (with about 120 personnel each) can provide Force Recon capabilities to marine units they are attached to.
The two Special Operations Battalions provide a combination of services roughly equal to what the U.S. Army Special Forces and Rangers do, as well as some of the functions of the Force Recon units. Eventually, there are to be nine companies in the two Special Operations Battalion. Not all of these Special Operations companies have become operational.
The marines finally got around to working with SOCOM in late 2005, when it was agreed that they would create a marine special operations command. The Marine Corps had long resisted such a step, largely because of its belief that marines are inherently superior warriors, capable of highly specialized missions. This attitude began to change during the fighting in Afghanistan, when marines were assigned to support SOCOM troops there.
As a result of that experience, marines were attached to SOCOM for liaison and observation purposes. In 2004, the marines organized a company sized unit of commandos, "Detachment One", using volunteers from their Force Recon troops, the closest thing the marines had to commandos. Detachment One was sent to Iraq, where it's performance convinced SOCOM that marines could operate at the SOCOM level.
The U.S. Marine Corps Special Operations Command (MARSOC) has now sent some of its 2,400 personnel on 31 deployments (in South America, the Caribbean, Africa, the Middle East, Central Asia and Southeast Asia) over the last two years, since it became "operationally capable." It's expected to be another two years before SOCOM (Special Operations Command) declares the marine unit "fully mission capable".