During the Persian Gulf War, Iran–Oman relations were damaged after Iran began running attacks on tanker movements in the Persian Gulf and placed anti-ship missile launchers along the Strait of Hormuz. The Gulf neighbors have since restored their ties and have conducted joint military exercises as recently as February 2011. Oman's leader Sultan Qaboos traveled to Iran in 2009 for the first time since Iran's 1979 revolution. Though on two occasions the U.S. has dispatched high-level officials to discuss Iran with Oman, the fact that Oman has avoided publicly expressing any concerns regarding Iran's nuclear program is likely a reason why the two states have managed to maintain strong ties.