The United Kingdom has announced it will deploy Royal Air Force Typhoon fighter jets to help defend Saudi Arabia from missile and drone attacks by Yemen’s Houthis, the armed group also known as Ansar Allah (Arabic for Supporters of God).

The jets will play a “defensive role”, the British Ministry of Defence (MoD) said in a statement on Tuesday, adding that they will not carry out attacks against the Iranian-backed armed group.

The move comes amid heavy fighting between the Houthis and Yemen’s internationally recognised government, which is backed by Saudi Arabia.

In recent weeks, the Houthis have carried out missile and drone attacks against the kingdom, including oil facilities and Riyadh’s main airport, while the Saudi-led coalition supporting the Yemeni government has launched air attacks on Houthi positions.

The UK’s decision to send jets to assist Saudi Arabia marks just the latest chapter in a partnership that stretches back more than a century, to a treaty signed during the First World War, years before the Saudi kingdom was founded.

So what is the UK sending, and how did the two countries become so closely bound?

Here’s what you need to know:

What is the UK sending?

Fighter jets, an A400M transport aircraft and advisers.

The ministry said it was also extending air-to-air refuelling, which it previously agreed to provide for Saudi air operations, including those to degrade Houthi military targets in Yemen.

How far back does the UK-Saudi relationship go?

To the First World War.

In December 1915, Sir Percy Cox, a senior British official in the Gulf, concluded the Treaty of Darin with King Abdulaziz Ibn Saud, then ruler of Nejd in central Arabia, according to India Office records held by the UK’s National Archives.

In return, he allied with Britain against the Ottoman Empire, and Britain backed him with cash and weapons.

In May 1927, Britain signed a new treaty with him at Jeddah, according to an India Office memorandum.

King Abdulaziz founded the Kingdom of Saudi Arabia in 1932.

When did UK-Saudi arms deals begin?

In the 1960s.

In May 1966, Saudi Arabia signed contracts to buy 40 Lightning fighter jets and 25 jet trainers from the British Aircraft Corporation, along with a radar system, according to a US Department of State memo from the time.

Even then, Yemen was part of the picture.

In 1962, the Mutawakkilite Kingdom of Yemen was overthrown in a military coup and the Yemen Arab Republic was established. Egypt sent troops to back the republican government, while Saudi Arabia and Jordan armed and funded royalist forces trying to restore the Imam. By 1966, the civil war had reached a stalemate.

Meanwhile, Britain was facing rebellion from Soviet- and Egypt-backed nationalist groups over its control of Aden and southern Yemen. Britain ultimately withdrew in 1967.

In 1966, Saudi Arabia’s defence minister, Prince Sultan, asked the UK to supply an RAF fighter squadron to fly under Saudi colours if fighting resumed in Yemen, according to declassified US State Department records.

Britain instead offered fighter jets flown by British pilots, and said it was ready to send an RAF squadron of Lightning interceptors for a short period if required.

In the end, Saudi Arabia accepted the jets and civilian pilots, and the RAF squadron was not needed, the records show.

BAE Systems, then the British Aircraft Corporation, says its ties with Saudi Arabia date back to 1966, and in 1973, the two governments signed a memorandum of understanding naming the company as prime contractor.

1980s and the Al-Yamamah deal

In 1985, the two governments signed an oil-for-arms agreement, known as Al-Yamamah, for Tornado and Hawk jets.

The Reuters news agency has described the Al-Yamamah deals as the largest export contracts in British history.

Saudi Arabia set aside up to 600,000 barrels of oil a day to pay for Tornado jets and other equipment.

The UK’s Serious Fraud Office investigated corruption allegations linked to the deal from 2004, but dropped the inquiry in December 2006, according to a House of Lords judgement.

The attorney general, Lord Goldsmith, cited the need to safeguard national security.

Has Britain fought from Saudi soil before?

Yes.

When Iraq invaded Kuwait in August 1990, King Fahd of Saudi Arabia asked friendly governments for help.

On August 11, 12 RAF Tornado fighters flew from Akrotiri in Cyprus to Dhahran in Saudi Arabia, according to the RAF Museum.

Further RAF Tornado detachments were set up at Tabuk in Saudi Arabia in October 1990, and at Dhahran in January 1991, the museum’s records show.

During the war, then-Defence Secretary Tom King told Parliament that Saudi Arabia had provided the UK with host-nation support.

He also reported that a Tornado based in the kingdom had gone missing, the fourth lost in enemy action.

British aircraft then patrolled a no-fly zone over southern Iraq, alongside United States and French jets, flying from Saudi bases until 2003, according to the US Air Force.

Where do the Typhoons come in?

In September 2007, Saudi Arabia agreed to buy 72 Typhoons from Britain, the UK MoD said at the time. The jets were to replace Tornadoes and other aircraft in the Saudi air force.

The deal was worth 4.43 billion pounds (then about $8.9bn).

BAE Systems, which builds the jets, called it the Salam Project.

Further RAF Tornado detachments were set up at Tabuk in Saudi Arabia in October 1990 and at Dhahran in January 1991.

In March 2018, during Crown Prince Mohammed bin Salman’s visit to London, the UK signed a memorandum of intent with Saudi Arabia to finalise the purchase of 48 more Typhoons, BAE Systems said in a statement to the London Stock Exchange.

But the deal stalled.

Germany, which helps build the Typhoon and has a veto over its exports, halted arms sales to Saudi Arabia after the killing of Saudi journalist Jamal Khashoggi, a columnist for The Washington Post who wrote critically of the crown prince and his policies, in 2018.

Berlin dropped its objection in January 2024, with then-Foreign Minister Annalena Baerbock saying the Middle East had become a completely different place since October 7, 2023, when southern Israel was attacked by Hamas and Israel launched its genocidal war on Gaza.

BAE said that year it was supporting the UK government in discussions with Saudi Arabia.

What about Yemen?

In June 2019, five years after the Houthis seized Yemen’s capital, Sanaa, triggering a brutal civil war, the UK’s Court of Appeal ruled that the government had acted unlawfully by licensing arms sales to Saudi Arabia for possible use in Yemen without assessing whether past incidents had breached international humanitarian law.

New licences were halted. In July 2020, then-Trade Secretary Liz Truss told Parliament they would resume, saying there was not a clear risk the arms would be used in a serious violation of the law.

The UK has also struck the Houthis directly. RAF Typhoons joined US attacks on Yemen in 2024 following Houthi attacks on Israel-linked Red Sea shipping in response to the bombardment of Gaza, according to the MoD.

Then, in September this year, Britain sent a Voyager tanker to assist Saudi Arabia with air-to-air refuelling of fighter jets. The planes it refuels are British-built Typhoons flown by the Saudi air force.