Operation Prime Chance - Execution

Execution

Soon afterward, operations began from the barges, dubbed Mobile Sea Bases (MSBs). They were set up as Naval Special Warfare Task Units (NSWTU) run by a SEAL commander and answering to the regional Naval Special Warfare Task Group. Their mission was to stop Iranian forces from mining the Persian Gulf or otherwise attacking shipping. Each mobile sea base had two detachments of Mark III patrol boats, a SEAL platoon, an EOD detachment, Marines to provide security, Army MH-6 and AH-6 Little Bird helicopter gunships and Black Hawk rescue birds, and Air Force combat controllers. Mobile Sea Base Hercules was manned by East Coast Naval Special Warfare units, including Patrol Boats 777 and 758 from Special Boat Unit 20 and Special Boat Unit 24. Mobile Sea Base Wimbrown 7 was manned by West Coast units, including Patrol Boats 753 and 757 from Special Boat Unit 13 and Patrol Boats 775 and 776 from Special Boat Unit 12.

The operation's most dramatic engagement was likely the 21 September 1987, attack on the Iran Ajr, an Iranian ship converted for use as a minelayer. Using night-vision devices, Army gunship crews watched the Iranian vessel lay several mines, then swooped in firing miniguns and rockets. A SEAL team boarded the vessel and quickly seized it. During the attack, five Iranians were killed and 26 were captured. Several Iranian sailors were rescued from the waters of the Persian Gulf after jumping overboard during the attack. After collecting intelligence data the SEALs and EOD scuttled the vessel the following day.

In January 1988, Task Force 118 arrived with OH-58D Kiowa Warrior helicopters.

Earnest Will ended about five months after the Iran-Iraq ceasefire began in July 1988. Wimbrown 7 soon returned to port, but Prime Chance patrols continued from Hercules until June 1989.