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Operation Prime Chance
Part of Iran-Iraq War
A U.S. Navy crewman stands atop the cabin of a PB Mark III patrol boat tied up to the oil rig service barge Wimbrown VII in the northern Persian Gulf. From lower to upper right, the barge is armed with an M-2 .50-caliber machine gun, a Mark 2 81mm mortar, and a Mark 19 40mm grenade-launcher.
Date August 1987 - June 1989 Location Persian Gulf Result U.S. victory Casus belli Mining of the U.S.-flagged Kuwaiti oil tanker al-Rekkah.
Combatants
United States Special Operations Command	Iranian Navy

An aerial view of the leased barge Hercules with three Mark III patrol boats and the tugboat Mister John H tied up alongside in the northern Persian Gulf.

Operation Prime Chance (August 1987-June 1989) was a United States Special Operations Command operation intended to protect U.S.-flagged oil tankers from Iranian attack during the Iran-Iraq War. The operation took place roughly at the same time as Operation Earnest Will (July 1987-December 1988), the largely Navy effort to escort the tankers through the Persian Gulf.

The two operations were intertwined — U.S. Army helicopters flew nighttime search-and-destroy missions from Navy frigates and destroyers and from two leased barges in the northern Persian Gulf. Navy SEALs operated from the barges as well. But while Earnest Will was the widely publicized reaction to Kuwaiti pleas for help, Prime Chance was secret. The Army helicopters flew at night, slipping to and from Navy flight decks under cover of darkness. The helicopter pilots often flew some 30 feet above the water, and became the first to use night vision goggles and forward looking infrared devices in combat. Tactics included using MH-6s as spotters for the more heavily armed AH-6s (for barge-launched missions), and using the warship's radar and that of their SH-60 Seahawk helicopters for the same purpose (on ship-launched efforts).^[1]

Planning and preparation for Prime Chance was launched soon after a tanker on the very first Earnest Will convoy struck a mine, which made it clear that more forces would be necessary to assure the safety of the civilian vessels. The Joint Chiefs of Staff launched a search for helicopter pilots who could fly at night from Navy ships, then set out to train them for the special requirements of the job. Helicopters from the Army's 160th Special Operations Aviation Regiment (Airborne) reached the Navy's command ship USS La Salle (AGF-3) in the Gulf on August 5, 1987. The detachment was divided into two teams, with call sign SEABAT and one MH-6, two AH-6s, aircrew, and maintainers. On August 8, one detachment participated in a convoy escort mission aboard La Salle. The other flew onto USS Klakring (FFG-42) to protect minesweeping tugboats operating in the narrow shipping channel west of Farsi Island. The following day, the La Salle detachment transferred to USS Jarrett (FFG-33) and escorted the convoy to the Gulf of Oman.^[1]

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 Gulf or otherwise attacking shipping. Each mobile sea base had two detachments of Mark III patrol boats, a SEAL platoon, Marines to provide security, Army MH-6 and AH-6 Little Bird helicopter gunships and Black Hawk rescue birds, and Air Force combat air 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.^[2]

The operation's most dramatic engagement was likely the September 21, 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 with miniguns and rockets blazing. A SEAL team boarded the vessel and quickly seized it. Several Iranian sailors were rescued from the waters of the Gulf after jumping overboard during the attack. The SEALs scuttled the vessel the following day.^[3]

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.^[2]

Units involved in Prime Chance include:

• 160th Special Operations Aviation Regiment (Airborne), aka the "Night Stalkers", the Army's elite special-operations flight squadron
• Task Force 118, a regular army aviation unit flying AH-58D Warrior helicopters whose mast mounted IR sights helped spot small boats. In 1990, the unit became 4th Squadron, 17th Cavalry Regiment, and then, in 1994, it became 4th Squadron, 2d Armored Cavalry Regiment^[4]
• Mobile Sea Base Hercules and Wimbrown 7, barges leased from an oil company for use by SEALs, Navy small-boat crews, and Army helicopters
• USS Deyo (DD-989)^[5]
• USS John A. Moore (FFG-19)
• USS Klakring (FFG-42)
• USS La Salle (AGF-3)
• USS Samuel B. Roberts (FFG-58)
• SEAL Team 1
• SEAL Team 2
• Special Boat Unit 12
• Special Boat Unit 13

• Operation Earnest Will
• Iran-Iraq War

• A warrant officer's personal TF118 narrative
• Attack on Iran Ajr
• Photos of the captured Iran Ajr, its mines, its sailors

• Report, Dr. John Partin, History and Research Office, USSOCCOM, Special Operations Forces in Operation EARNEST WILL/PRIME CHANCE I, April 1998.
• Book, Inside the Navy Seals, By Gary Stubblefield.
• Peniston, Bradley (2006). No Higher Honor: Saving the USS Samuel B. Roberts in the Persian Gulf. Annapolis: Naval Institute Press. ISBN 1-59114-661-5.  (Briefly discusses TF118 operations from a U.S. Navy frigate)
• Wise, Harold Lee (2007). Inside the Danger Zone: The U.S. Military in the Persian Gulf 1987-88. Annapolis: Naval Institute Press. ISBN 1-59114-970-3.