Why are Iran’s top officials so confident they can defeat a US invasion?

Most world leaders would shudder at the thought of soldiers from the most expensive military force in history bearing down on their borders.

But with thousands of US Marines gathering near Iran in the past week, Tehran has instead urged the US to land on its shores, saying via state-run news: “Come close, we are waiting for you.”

So why is the country confident it could ward off a US invasion?

Former ADF officer turned UNSW senior lecturer Andrew Maher told 7NEWS.com.au the country’s nerve comes from spending decades developing a defence strategy built specifically to disrupt a larger military force.

One of Maher’s roles in the army was to command a platoon of soldiers in Afghanistan in 2007, a war which he believes Iran was watching with a keen eye to learn how to oppose the US military.

“It was a live experiment,” Maher said.

That experiment led to Iran implementing three key tools it is confident would make a US invasion costly not only in terms of human life, but also the government’s war chest.

Iran’s ‘mosaic’ defence

One of Iran’s major changes followed the rapid collapse of the Iraqi government after its leadership and command structure were targeted in 2003.

In response, Iran decentralised its military in 2008 to introduce the Provincial Commands of the Islamic Revolutionary Guard Corps (IRGC) — described as a “mosaic defence”.

The Provincial Commands are granted limited autonomy over regions of Iran, meaning they could continue to mount a defence if heads of the military are killed during conflict.

Instead of trying to face an invading force head-on, the strategy instead emphasises operational continuity which increases the time and cost an opposing force would spend on the conflict.

Maher said there are hundreds of militia-like forces, part of the Basij, sprinkled across Iran which are “there to wage an insurgency in the event of an invasion”.

The number of commands makes it harder to claim a complete military victory over Iran, as each force can pull leaders from its ranks and continue to wage a defence all while their opposing force would continue to bleed resources, funds and time.

Drones and cheap technology

Another aspect of wars in Afghanistan and Iran were Al-Qaeda and Taliban forces using cheap yet effectives weapons and explosives to counter the massive costs of the US and allied war machines.

One of the most destructive weapons used were explosively formed penetrators (EFP), or roadside bombs, which wreaked havoc on US vehicles across the region.

“The cost of armouring those vehicles is running into the billions of dollars to protect their force from this relatively cheap explosive at about $50 (each),” Maher said.

“Iran saw this action reaction cycle and how that cascaded through to have an impact on the US willingness to maintain the war efforts.”

Iran’s version of cheap weaponry is its mass-produced Shahed drones which, depending on the model, can travel more than 1000km and carry more than 90kg of explosives.

While costing significantly more than EFPs at about $40,000 each, they are just a fraction of the US’ Tomahawk cruise missiles which cost about $3.6 million each.

The waves of drones launched across the region in the opening month of war has become a serious problem for the US and Iran’s neighbours in the Persian Gulf as air-defence systems struggle to shoot down each unit.

Those that got past have struck military bases and civilian infrastructure such as hotels, airports and gas fields.

Funding foreign militia groups

Iran expanded on its mosaic defence strategy by funding and gaining the loyalty of non-state armed groups in the region, particularly during the 2010s.

Maher said Iran’s support of groups such as Hezbollah, Hamas, ISIS, Houthis and the Taliban would mean groups experienced in fighting the US in the Middle East would be able to support in the event of an invasion.

“Iran has had a state level strategy of using non-state armed groups as a component of its national security strategy, arcing back 40 odd years,” he said.

“They have been creating power through this network of proxies to try to have a level of hegemonic power in the Middle East that ensures a level of state security.”

While the mosaic strategy is to defend, Iran’s network of loyal militias is instead meant to overwhelm an opposing force with attacks from across the region and opening up new war fronts to thin them out.

“They give Iran an ability to create a horizontal escalation challenge and shifting the point where military actions are occurring,” Maher said.

Following the first US-Israeli attacks on Iran which killed Supreme Leader Ayatollah Ali Khamenei, Hezbollah launched attacks just days after while Iraqi forces and the Houthis joined weeks later.

“They’ve got plenty of experience in waging that type of conflict and when we are talking about prolonged insurgencies, they require a lot of resources to combat them,” Maher said.

In a national address, US President Donald Trump said US forces would attack Iran hard in coming weeks and send the country “back to the Stone Age” before he would leave the war.

But Maher warned both Trump and Iran could be puffing out their chests to try to intimidate each other.

“This has kind of been baked in from trying to analyse Russian activities over the last few years,” he said.

“You need to be very, very circumstantially speculative about what leaders say.

“They’re trying to do multiple things: misleading the adversary, maintain a domestic constituency or potentially also signal an ability to shift and pivot.

“So I have to admit, I don’t place what Trump has to say front and centre in how I analyse these conflicts.”

He said the more important aspect is the heavy losses Iran has suffered in the first month of war.

“Anywhere up to 70 per cent of different Iranian military capabilities, such as the Iranian Navy, or their missile systems have been reduced or taken off the battlefield,” Maher said.

“It doesn’t really matter how Trump is framing the conflict, when you’re taking 70 per cent of the military capability off the battlefield that has a significant effect.”