Tensions between Iran and the United States have simmered for decades since the 1979 Islamic Revolution, but in recent weeks their longstanding tensions appear to be boiling over.

Key points: Tensions between Iran and the US have raised fears of another Middle Eastern war

Tensions between Iran and the US have raised fears of another Middle Eastern war At least 60,000 US troops are deployed across the region, encircling Iran

At least 60,000 US troops are deployed across the region, encircling Iran Iran has few overseas military facilities to match the US military's dominant position

This week, Tehran launched attacks against two large airbases hosting US and coalition forces in neighbouring Iraq, in retaliation for the US's unilateral assassination of Iranian General Qassem Soleimani and Iraqi militia leaders last week.

Soleimani was revered in Iran, whom the US claimed was plotting "imminent attacks" against its personnel in the Middle East as the reason for the killing, without specifying what they were.

In the days after the US strike, observers in capitals around the globe had rung the alarm about World War III, while administrations in Tehran and Washington continued to ratchet up the war-mongering rhetoric.

US President Donald Trump has threatened to destroy 52 Iranian sites including those of cultural significance, while Iran's leader — Ayatollah Ali Khamenei — has said the strikes were the "weakest" of its revenge scenarios.

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Another layer of complexity was added as Canadian and allied intelligence alleged that Iran was responsible for shooting down a commercial passenger plane amid the missile attacks on Iraq.

While Prime Minister Justin Trudeau admitted that it could have been "unintentional", he nonetheless called for a thorough investigation into the incident that killed all 176 people onboard.

While it appears the dust may be settling on the militarised rhetoric spouted on both sides in recent days, one thing is clear: the US has a far greater chance of overwhelming Iran in any direct armed conflict.

Globally, the publicly-known number of US bases nears 800.

Iran is encircled by numerous American military facilities ranging from fully-operational bases, to airfields, to surveillance sites dotted across the Middle East.

The map above shows major US military facilities in Iran's neighbourhood, in countries including Saudi Arabia, Oman and the United Arab Emirates (UAE) — and they're just the ones we know about based on data from the American Security Project, US Government, and Australian Defence Force.

International peacekeeping bases are not included, nor are covert US bases for which there is no significant proof of existence.

Military installations surrounding Iran include fixed and transient US sites, as some facilities are designed as temporary, such as those designed to house US and coalition forces in Afghanistan.

Kuwait, Qatar and Bahrain host some of the largest number of US personnel in the Middle East. ( US Navy: Jayme Pastoric )

The US also has the ability to move its aircraft carriers near the waters of a belligerent — like it did in the lead-up to the 2003 Iraq War.

Naval Support Activity Bahrain is one such fixed-location, which is close to Iraq's Khalifa Bin Salman port.

It houses the US Navy's 5th fleet, while it is also capable of berthing US aircraft carriers.

Outside of the Middle East, the US also has assets dotted in strategic locations in the middle of seemingly open oceans.

The US Naval Support Facility of Diego Garcia is one such example, which is leased from the UK as the isolated atoll forms part of the British Indian Ocean Territory.

It provides logistical support to US forces deployed to the Indian Ocean and Persian Gulf, which in recent days, has hosted six B-52 bomber aircraft in response to heightened tensions with Iran, according to CNN.

60,000 US troops in Iran's immediate region

Having fought numerous wars in the Middle East since 2001 — at an estimated cost of $US6.4 trillion ($9.3 trillion) — the US has built up a massive military presence in the Middle East in its own right.

Presently, at least 60,000 troops are currently stationed around the Middle East, according to US Central Command.

The map above shows how the US troops are distributed across the region, according to figures from the Federation of American Scientists and International Crisis Group.

Kuwait has the lion's share of troops in the region, with more than 13,000 troops stationed in the tiny Middle Eastern state.

Qatar, Bahrain and the UAE also host thousands of troops respectively.

The US military has been involved in operations across the Middle East for decades. ( US Air Force )

While at least 5,000 troops are deployed in Iraq in an advisory capacity, this number may soon change as the Iraqi parliament voted to boot all foreign forces out of the country in retaliation of the killing of Soleimani.

Iran has nowhere near the amount of foreign military facilities as the US does. The few that it does have are located in Syria, Iraq, Lebanon and Eritrea respectively.

However, the US and its allies have alleged that Iran's armed forces have been complicit in arming and financially aiding militia groups in the Middle East, including Iraq's Kataib Hezbollah, Yemen's Houthi rebels, and the Palestinian territories' Hamas.

Presently, more American troops are being sent to the Middle East, while Tehran shows no signs of dampening its militarised rhetoric.

While it is anticipated that diplomacy is humming in the background behind America and Iran's public statements, it remains unclear if the US-Iranian's game of brinkmanship will cease for the time being.

Additional reporting by Max Walden.