According to U.S. Defense officials, Iran attempted to conduct a test launch of a cruise missile from a submerged submarine in the Strait of Hormuz on Tuesday. The test ended in failure.

Iran, which has received multiple warnings from the Trump White House regarding their efforts to increase their potentially nuclear-capable ballistic missile arsenals, conducted their first successful test of a submarine-based missile platform in February of this year. This week’s test may have been their first effort at launching that missile design from a submerged vessel, however.

Although official confirmation has not been forthcoming, it seems likely that the missile test was conducted using the Hormuz 2, Iran’s first naval missile. Iran claims the missile has a range of approximately 180 miles and is built with materials and expertise sourced entirely within the nation’s own borders. February’s successful test saw a Hormuz 2 destroying a floating barge located some 150 miles away from the launch site, indicating that Iran now possesses the ability to engage naval vessels beyond the horizon and without line of sight.

The submarine used to launch the missile, known as the Yono or Ghadir class, was first designed and produced in North Korea in 2004. Iran began producing its own copies of the North Korean submarine in 2005, making Iran and North Korea the only nations to use this submarine in their active naval fleets. The 130-ton displacement subs have been given the moniker “midget” submarines because of their size, and boast a maximum speed of only 11 knots (or a little less than 13 miles per hour).

At 95 feet long and only about nine feet wide, the Ghadir-class submarine is said to be equipped with sonar-evading technology, and must have undergone a fair amount of internal revisions in order to carry and fire cruise missiles. The North Korean Yono-class platform it is based on is equipped with only two torpedo tubes and no missile-launching capabilities. Iran is said to maintain 20 of these vessels in its fleet, twice that of the North Koreans, and they are often used to deliver special operations personnel.

Because of its size, the Ghadir-class submarines are generally considered to be coastal or littoral combat submarines, and not particularly well-suited for operations in open waters.

In March of this year, CENTCOM Commander General Joseph Votel appeared before the House Armed Services Committee to testify that Iran “poses the greatest long-term threat to stability” in the Middle East. President Trump, who has been critical of a nuclear deal established between Iran, the Obama administration, and a number of international partners, has been reviewing the U.S. strategy on Iran and his willingness to maintain America’s ties to what he refers to as a “bad deal.” President Trump believes the deal, which was intended solely to curb Iran’s nuclear ambitions, should have involved language addressing Iran’s support of terrorism and domestic human rights abuses.

The Strait of Hormuz, a strategically important waterway separating the Persian Gulf from the open ocean, has been the site of numerous aggressive interactions between Iranian vessels and the United States Navy, the most recent of which occurred just last week, when the USS Mahan was forced to change course in order to avoid a collision with a fast-attack craft belonging to the Iranian Islamic Revolutionary Guard. Previous altercations have resulted in the USS Mahan firing warning shots at similar fast-attack boats as they have approached it with weapon systems manned.