Following repeated Iranian threats to block shipping in the strategic Strait of Hormuz, an international fleet of 35 navy ships are in the Gulf for the world’s largest naval anti-mine exercise.

Led by Britain’s Royal Navy, representatives from 41 different navies are spending three weeks practicing the detection and clearance of deadly mines. The International Mine Countermeasures Exercise (IMCMEX) 13 will continue through the end of May.

While Iranian officials warned against “provocations” in the Gulf, American defense officials said there was no way the exercise could be interpreted as being offensive.

“Mine counter-measure activity is an inherently defensive exercise, there cannot be a misinterpretation that it’s an offensive exercise in any way,” said U.S. Navy Vice Admiral John Miller, head of the US Fifth Fleet based in Bahrain.

Ships will also carry out exercises to protect oil installations and escort convoys of merchant ships in the area that transports on the sea 30 percent or more of the world’s crude oil supplies.

During the Iran-Iraq war in the 1980s, Iran often targeted oil tankers and laid anti-shipping mines that hit both civilian and military vessels in what was dubbed the “tanker war.” Several different naval forces at the time (U.S., British, French Belgian, Dutch, and others) cleared hundreds of mines.

Iran is estimated to have at least 2,000 anti-shipping mines, and the exercise includes sophisticated underwater robot drones that hunt the lethal mines that can be positioned anywhere from just below the surface of the water to the sea floor.

[Photo: Konabish / Flickr]