Israel/US-Iran conflict 2026: Background and UK response

Note: This research briefing is not intended to provide detailed information on fast-moving events. Due to the ongoing conflict and restricted internet and media access within Iran, civilian and military casualties and reports on specific events can be difficult to verify.

This is a summary of a fuller briefing, which can be downloaded as a PDF.

On 28 February 2026, Israel and the United States began a series of strikes against Iran. They said they aimed to induce regime change and target its nuclear and ballistic missile programme. A conditional ceasefire was declared on 8 April. Talks are being mediated by Pakistan].

In response to the attack, Iran launched a series of counter-strikes against Israel, US military bases in the region, and military and civilian locations in Arab states, many of which house US forces. UK bases in Bahrain, Qatar and Cyprus were attacked and the RAF was deployed in a defensive capacity.

This briefing sets out US and Israeli statements on their decisions to launch the attacks, the Iranian regime’s response, the death of Supreme Leader Ali Khamenei and selection of his son as his successor, and UK actions and response to the conflict. This includes information on UK defensive military action, diplomatic initiatives and UN action, and responses within the UK Parliament. A separate briefing describes talks on an agreement in 2026.

Iran’s internal and regional position is weak

The attacks came when the Iranian regime was arguably at its weakest point for some years:

• There were extensive protests in Iran in early 2026, motivated by a weakened economy as well as struggling infrastructure, illustrating the regime’s weakened legitimacy within the country. The protests were put down with extensive use of force. Arrests have continued in the conflict.
• Many of Iran’s regional allies have been significant weakened, primarily by Israeli military action from 2023.
• Israeli military strikes in 2024 and joint strikes with the US over 12 days in 2025 undermined Iran’s defences and nuclear programme.
• Iran’s counter-strikes on Arab Gulf states in 2026, who have sought to deepen relations in recent years, may also leave it further isolated.

The attacks also follow the failure of indirect negotiations in February 2026 on a new agreement to curtail Iran’s nuclear programme. The mediating Omani foreign minister had stated significant progress, with Iran willing to make concessions, but President Trump said he was “not thrilled” with the talks.

Statements by US, Iran and Hezbollah actions

The US said its attacks were in line with the right to self-defence under the UN charter until the UN Security Council takes action. It has accused Iran of continuing to advance its nuclear and ballistic missile programmes. President Trump has called for the overthrow of the governing regime but has since said regime change has occurred, though he says he distrusts Iran’s new leader.

The Iranian Government condemned the US-Israel attacks as a breach of the UN charter and said it would exercise the right to self-defence. Iranian officials said that Israel and US bases across the region would be targeted.

Iran-backed Hezbollah in Lebanon has also attacked Israel in support of Iran, causing the Lebanese Government to ban Hezbollah’s military activities and Israel to launch military operations. Since the 2023/24 Israel-Hezbollah conflict, the Lebanese Government has sought to disarm Hezbollah, but the group retains extensive weaponry and some support in Shia communities. In mid-April, separate talks arranged a ceasefire, extended to late May.

The Strait of Hormuz

In response to the attacks, Iran said it would shut the Strait of Hormuz, a major oil and trading route. While a small number of ships permitted by Iran have continued to use the strait, almost all shipping has ceased.

The US responded by temporarily removing sanctions on some Russian oil and Iranian oil already in transit. Exemptions for Iran expired in mid-April. The 32 members of the International Energy Agency, including the UK, have also released 400 million barrels of oil in an attempt to lower prices.

On 13 April, the US launched a counter-blockade of the Strait, targeting all ships seeking to reach Iranian ports. The reopening of the strait is a major issue in the Pakistani-mediated talks. Iran has threatened military action if the US blockade does not end. President Trump has threated extensive attacks on Iranian infrastructure if Iran does not reopen the Strait.

The separate Library briefing on the strait sets out international initiatives.

UK response and defensive military action UK calls for ceasefire to be adhered to

On 28 February 2026, in a joint statement with the leaders of France and Germany, the Prime Minister Sir Keir Starmer condemned the Iranian counter-strikes and called for a resumption of diplomacy. The leaders reiterated their shared positions that the Iranian regime should end its nuclear programme, curtail its ballistic missile programme, end the repression of Iranians, and stop its support for armed groups abroad. The Prime Minister said he did “not believe in regime change from the skies”. The government also called for an end to military operations in Lebanon by Israel and Hezbollah.

UK military operations are defensive

The UK did not participate militarily in the strikes. UK aircraft have been deployed in a defensive role to intercept missiles and projectiles, including in Qatar, Jordan, Iraq and Cyprus. Among the measures the UK has taken include deploying HMS Dragon to Cyprus, four additional jets to Qatar and air defences to Bahrain, Kuwait and Saudi Arabia.

On 1 March 2026, the Prime Minister also said that the US could use UK military bases for a “specific and limited defensive purpose”, which he said was to “destroy the [Iranian] missiles at source”. On 20 March the government said that US use of the bases also includes “US defensive operations to degrade the missile sites and capabilities being used to attack ships” in Hormuz. Bases to be used are Diego Garcia (British Indian Ocean Territory/Chagos Archipelago) and RAF Fairford (Gloucestershire).

The government published summary legal advice on its decision and the continuing RAF operations, saying the actions are in self-defence.

March 2026 UN Security Council resolution

On 11 March, the UN Security Council passed a resolution demanding the end of attacks by Iran and its proxies against Arab states and civilians and “reaffirming” the right of ships to traverse the Strait of Hormuz. This was first proposed by the Arab Gulf states. China and Russia abstained on the resolution. The UK voted in favour of the resolution.