U.S. Special Operations Forces (SOF): Background and Issues for Congress [Updated March 28, 2019] [open pdf - 913KB]
From the Document: "Special Operations Forces (SOF) play a significant role in U.S. military operations and, in recent years, have been given greater responsibility for planning and conducting worldwide counterterrorism operations. U.S. Special Operations Command (USSOCOM) has about 70,000 Active Duty, National Guard, and reserve personnel from all four services and Department of Defense (DOD) civilians assigned to its headquarters, its four service component commands, and eight sub-unified commands."
CRS Report for Congress, RS21048
Congressional Research Service: https://crsreports.congress.gov/