The destroyer USS Bainbridge transits the Suez Canal in May. (Jason Waite/U.S. Navy) (MCSN Jason Waite/U.S. Navy)

Rising tensions that, according to President Trump, left the United States just short of open conflict with Iran this week highlight a grim reality that the Pentagon has coped with for years: While the U.S. military outguns Iran, Tehran could still make even a limited war painful.

Iran’s military has more than 700,000 troops, including a conventional army of about 350,000 soldiers, according to a Congressional Research Service report published last month. That’s not counting the Islamic Revolutionary Guard Corps, a specialized force comprising another 125,000 troops in its army and 20,000 personnel in its navy, the CRS report said.

It’s the IRGC that has created friction between the United States and Iran. The force, designated a foreign terrorist organization by the administration in April, patrols the strategically important Strait of Hormuz, oversees Iran’s ballistic missile programs and claimed responsibility for launching the missile that downed a U.S. RQ-4 surveillance drone over the Gulf of Oman early Thursday, prompting the Trump administration to plan a retaliatory strike before the president halted it late in the day.

A review of Iran’s weapons shows that many of them are “obsolete, obsolescent, or of relatively low quality,” according to a 2018 report by the Center for Strategic and International Studies. But the report adds that Tehran’s ballistic and cruise missiles, air defenses and use of proxy forces can “scarcely be ignored.”

Jim Stavridis, a retired U.S. admiral, said Iran has "exceptionally strong" assymetric warfare capability, in which one belligerent in conflict has greater ability than another.

“Cyber, swarm small-boat tactics, diesel submarines, special forces, and surface-to-surface cruise missiles are all high-level assets,” he said. “They are also very experienced at employing them in the demanding environment of the Middle East. They would pose a formidable challenge to U.S. forces, although we would ultimately prevail in any confrontation of course.”

A senior U.S. defense official, speaking on the condition of anonymity due to the matter’s extreme sensitivity, said Friday that ships accompanying the aircraft carrier USS Abraham Lincoln were poised to strike if called upon. They included the USS Bainbridge, a destroyer, and the USS Leyte Gulf, a guided-missile cruiser, both of which can carry Tomahawk missiles, the official said.

U.S. military officials on Friday declined to say whether the Lincoln and its accompanying ships are on standby waiting to carry out an operation, or whether a strike was imminent.

“The U.S. Central Command retains a robust military capability in the region that is ready to respond to any crisis,” said Army Lt. Col. Earl Brown, a military spokesman. “The United States does not seek conflict with Iran, but we are postured and ready to defend U.S. forces and interests in the region.”

Among the weapons that Iran possesses are antiaircraft missile systems such as the S-300, which can target objects at altitudes of 15 miles. Tehran also has a fleet of more than 300 aircraft, though nothing nearly as advanced as what the U.S. Air Force flies. The aircraft include Russian-made MiG-29 fighters and Su-24 bombers, and legacy American aircraft that the Pentagon has retired, such as the F-4. Iran bought them from the United States before its 1979 revolution, according to CRS.

At sea, Iran’s navy is believed to operate a fleet that includes more than 100 vessels, about half of which are small, quick-moving vessels that would not stand up well to American destroyers but could grind maritime traffic to a halt by laying mines and harassing commercial ships.

It is the actions of the IRGC and Iran’s proxy forces that have alarmed U.S. officials. The U.S. government has attributed numerous attacks to them globally over the past 20 years, and the Pentagon said this year that it believed Iranian proxy forces were responsible for the deaths of at least 608 U.S. troops in Iraq during the eight-year war spawned by the American invasion in 2003.

Early this week, the Pentagon said it was deploying 1,000 more troops to the Middle East to deter Iran. After a few days, it clarified that those forces include a Patriot battalion, which is used for air defenses, manned and unmanned surveillance aircraft, fighter jets and support planes, and “other deterrence capabilities.”