Here’s a look at Iran’s military and its capabilities.

Why is Iran’s military relevant right now?

Israeli officials had said they would respond to any attack by Iran with a counterattack, which could prompt further retaliation from Iran and possibly expand into a wider regional war. There is even a chance that a conflict of that sort could drag in the United States, although Washington has made clear it had nothing to do with the Damascus attack.

Analysts say that Iran’s adversaries, primarily the United States and Israel, have avoided direct military strikes on Iran for decades, not wishing to tangle with Tehran’s complex military apparatus. Instead, Israel and Iran have been engaged in a long shadow war via air, sea, land and cyberattacks, and Israel has covertly targeted military and nuclear facilities inside Iran and killed commanders and scientists.

“There is a reason Iran has not been struck,” said Afshon Ostovar, an associate professor of national security affairs at the Naval Postgraduate School and an expert on Iran’s military. “It’s not that Iran’s adversaries fear Iran. It’s that they realize any war against Iran is a very serious war.”

What sort of military threat does Iran pose?

The Iranian armed forces are among the largest in the Middle East, with at least 580,000 active-duty personnel and about 200,000 trained reserve personnel divided among the traditional army and the Islamic Revolutionary Guards Corps, according to an annual assessment last year by the International Institute for Strategic Studies.

The army and the Guards each have separate and active ground, air and naval forces, with the Guards responsible for Iran’s border security. The General Staff of the Armed Forces coordinates the branches and sets the overall strategy.

The Guards also operate the Quds Force, an elite unit in charge of arming, training and supporting the network of proxy militias throughout the Middle East known as the “axis of resistance.” These militias include Hezbollah in Lebanon, the Houthis in Yemen, militia groups in Syria and Iraq and Hamas and Palestinian Islamic Jihad in Gaza.

The commander in chief of Iran’s armed forces is the supreme leader, Ayatollah Ali Khamenei, who has the last word on all major decisions.

While the proxy militias are not counted as part of Iran’s armed forces, analysts say they are considered an allied regional force — battle ready, heavily armed and ideologically loyal — and could come to Iran’s aid if it was attacked.

“The level of support and types of systems Iran has provided for nonstate actors is really unprecedented in terms of drones, ballistic missiles and cruise missiles,” said Fabian Hinz, an expert on Iran’s military at the International Institute for Strategic Studies in Berlin. “They could be viewed as part of Iran’s military capability, especially Hezbollah, which has the closest strategic relationship with Iran.”

What kinds of weapons does Iran have?

For decades, Iran’s military strategy has been anchored in deterrence, emphasizing the development of precision and long-range missiles, drones and air defenses. It has built a large fleet of speedboats and some small submarines that are capable of disrupting shipping traffic and global energy supplies that pass through the Persian Gulf and the Strait of Hormuz.

Iran has one of the largest arsenals of ballistic missiles and drones in the Middle East, Mr. Ostovar said. That includes cruise missiles and anti-ship missiles, as well as ballistic missiles with ranges up to 2,000 kilometers, or more than 1,200 miles. These have the capacity and range to hit any target in the Middle East, including Israel.

In recent years, Tehran has assembled a large inventory of drones with ranges of around 1,200 to 1,550 miles and capable of flying low to evade radar, according to experts and Iranian commanders who have given public interviews to the state news media. Iran has made no secret of the buildup, displaying its trove of drones and missiles during military parades, and has ambitions to build a large export business in drones. Iran’s drones are being used by Russia in Ukraine and have surfaced in the conflict in Sudan.

The country’s bases and storage facilities are widely dispersed, buried deep underground and fortified with air defenses, making them difficult to destroy with airstrikes, experts say.

Where does Iran get its weapons?

International sanctions have cut Iran off from high-tech weaponry and military equipment manufactured abroad, like tanks and fighter jets.

During Iran’s eight-year war with Iraq in the 1980s, few countries were willing to sell weapons to Iran. When Ayatollah Khamenei became Iran’s supreme leader in 1989, a year after the war ended, he commissioned the Guards to develop a domestic weapons industry and poured resources into the effort, which was widely reported in the Iranian news media. He wanted to assure that Iran would never again have to rely on foreign powers for its defense needs.

Today, Iran manufactures a large quantity of missiles and drones domestically and has prioritized that defense production, experts said. Its attempts to make armored vehicles and large naval vessels have met with mixed results. It also imports small submarines from North Korea while expanding and modernizing its domestically produced fleet.

How do other countries see Iran’s military, and what are its weaknesses?

Iran’s military is viewed as one of the strongest in the region in terms of equipment, cohesion, experience and quality of personnel, but it lags far behind the power and sophistication of the armed forces of the United States, Israel and some European countries, experts said.

Iran’s greatest weakness is its air force. Much of the country’s aircraft date from the era of Shah Mohammed Reza Pahlavi, who led Iran from 1941 to 1979, and many have been disabled for lack of spare parts. The country also bought a small fleet from Russia in the 1990s, experts said.

Iran’s tanks and armored vehicles are old, and the country has only a few large naval vessels, experts said. Two intelligence gathering vessels, the Saviz and Behshad, deployed on the Red Sea, have aided the Houthis in identifying Israeli-owned ships for attacks, American officials have said.

Will Israel’s attack disrupt Iran’s military?

The assassinations of the senior military officials are expected to have a short-term impact on Iran’s regional operations, having eliminated commanders with years of experience and relationships with the heads of the allied militias.

Nevertheless, the chain of command for the armed forces inside Iran remains intact, experts say.