Time | Rebecca Collard : When Iranian state television broadcast images of the destroyed U.S. spy drone it shot down over the strait of Hormuz it served two purposes.

One was intended to prove the RQ-4 Global Hawk had illegally entered Iranian airspace, contradicting U.S. claims the $170 million unmanned aircraft had been flying in international airspace. The other was to display Iran�s impressive anti-aircraft capabilities.

The RQ-4 Global Hawk is one of the U.S.�s most sophisticated intelligence-gathering devices. It can peer into countries from outside their borders and is able to fly as high as 60,000 feet, a greater altitude than many fighter jets. Yet Iran�s elite Revolutionary Guard Corps (IRCG) was able to detect it, and shoot it down with a surface-to-air missile fired by the Iranian-made Khordad 3 air defense system.

As tensions continue to escalate in the Persian Gulf, President Donald Trump said on Tuesday that if war breaks out with Iran �You�re not going to need an exit strategy. I don�t need exit strategies.�

But that could be underestimation of the cost of war with one of the Middle East�s most powerful militaries, which has well-equipped allies and proxies across the region.

Iran is estimated to have around 700,000 military and security forces, according to a Congressional Research Service (CRS) report from May. That includes about 350,000 regular ground troops.

But it was the parallel forces of Iran�s elite Revolutionary Guard, which number around 130,000, that took credit for downing the RQ-4 Global Hawk. The US has also accused the IRGC of carrying out attacks on tankers in the Gulf of Oman.

Iran�s military arsenal is significant enough to defend itself against its neighbors, but no match for the U.S. might in conventional warfare. However, the country�s significant and seemingly advanced surface-to-air missile (SAM) capabilities would complicate U.S. airwar attempts.

On top of the Iranian-made SAMs, the Islamic Republic has batteries of advanced Russian-made S-300 missile defense systems and even U.S. weapons. Until the 1979 uprising and overthrow of Shah Mohammed Reza Pahlavi, the U.S. was the largest provider of weapons to Iran. The country purchased more U.S. military equipment during the Iran-Contra affair in the early 1980s, including U.S. I-Hawks surface-to-air missiles.

Iranian leaders have made it clear that if the U.S. attacks Iran the conflict would spread across the region. Iran is in a unique position to do that, having cultivated a network of allied militias via the IRGC which already pose a threat to the U.S. and its allies.

Yemen�s Houthi rebels have stepped up attacks on U.S. ally Saudi Arabia in recent months, lobbing rockets across the border and increasingly using drones to attack Saudi military bases and airports. In the Gaza Strip, Iran has armed and funded the Palestinian Islamist movement Hamas, which has bragged about an increasing arsenal in recent years, and moved from primitive projectiles to much longer range missiles.

In Iraq, as tensions rose between the U.S. and Iran, militants fired more than a dozen rockets at bases hosting U.S. personnel and other sites of American business interest. Michael Knights, a senior fellow of The Washington Institute, says the rockets were �aimed to miss��only sending a message. But not because they aren�t capable.

�In terms of capabilities, these movements have killed well over 600 Americans in the past in Iraq, using advanced roadside bombs, rockets, snipers and other attacks,� says Knights. �It doesn�t take a lot of people to cause a lot of damage in Iraq.�

Although levels of loyalty and alliance to Tehran vary, many of Iraq�s most powerful militias have already been clear they want the U.S. military out of Iraq. �But many of these groups will not attack unless they get the green light from Iran,� says Renad Mansour, who is a fellow with Middle East and North Africa Programme at Chatham House.

The U.S. has tried to stem the flow of money from Iran to the militas it supports. In a briefing on Monday, the U.S. Special Representative Brian Hook repeated the U.S. assertion that sanctions �have weakened Iran�s military spending and also its ability to support its proxies.� Hook said in the call that Iran had decreased its military budget by 29 percent this year, and 10 percent the year before.

That appears to have had a knock-on effect on Hezbollah, the Lebanese political party and militia group closely linked to Iran. In recent months, Hezbollah�s leader, Hassan Nasrallah, has called for an �economic jihad� asking followers to give cash, and donation boxes can be found in shops and public venues in Lebanon.

But Amal Saad, professor at the Lebanese University, says the group has always sought donations and that tightening of funds seems to have affected the group�s charity work, not its military operations. She sees no evidence of eroding Hezbollah military capabilities, she says.

Yet while Hezbollah relies heavily on Iranian funds and weapons, Saad says the relationship has become more of an alliance than proxy-patron, especially with the war in Syria. �They peddle this myth that Iran makes a call and everyone runs � to carry out its orders and do its bidding,� says Saad. �They�re not puppets.�

That does not mean Hezbollah, or other regional militia, will sit still if the US attacks Iran. Groups like Hezbollah, she says, see the threat to Iran as �existential,� and share national interests and security concerns.

It�s also not clear the Pentagon assessment of an under-funded Iranian military is accurate. The CRS report from last month says Iran�s 2018-2019 defense budget had in fact risen to $25 billion dollars, �up from about $23 billion in 2017.�