The HMS Pembroke and HMS Grimsby left their port in Scotland to relieve their sister ships, HMS Blyth and HMS Ramsey, which were stationed in the Gulf for the past 27 months.
The Sandown-class Pembroke and Grimsby mine hunters are equipped with fiberglass hulls, making them capable of entering waters other classes cannot, the Ministry of Defense said.
"Modern mines are cheap to produce and extremely dangerous," said Royal Navy Cmdr. Henry Merewether. "We cannot put a value on the work that these small ships are doing."
British forces are rotated by air to the arriving ships every five to eight months, meaning the British Royal Navy has a constant presence in the Persian Gulf.