Iranian forces fired what military officers said was a new generation of its Thunder surface-to-air midrange missile on Monday, December 31, during a wide-ranging naval exercise in international waters to the south of the country, The New York Times reported. The missiles were fired on the fourth day of a six-day naval exercise that started Friday and included drills using Iranian-made drones and submarines. In addition, Iran deployed warships and helicopters to escort commercial ships and oil tankers as part of a drill meant to show the country’s ability to combat piracy, the official Islamic Republic News Agency said. The exercise included activity in the Strait of Hormuz, a strategic waterway through which one-fifth of the world’s oil supply passes and which Iran has previously threatened to close in retaliation for Western sanctions over its nuclear program.