Iran’s nuclear ambitions have been at the core of fears over a heightened risk of conflict in the Middle East for more than a decade.
Iran had a peaceful nuclear programme for many years, but in the early 2000s concerns were raised that it was developing technology that could create nuclear weapons – despite the country being a signatory of the Non-Proliferation Treaty.
Not long after the firebrand then-president Mahmoud Ahmadinejad made a series of bold claims about uranium enrichment, the first of a number of UN resolutions was passed, aimed at forcing Iran to backpedal.
Diplomacy between Iran and the West went into the freezer for several years after the two sides became locked in a stand-off over Tehran’s claim that any programme it had was for purely peaceful purposes.
At the same time, Mr Ahmadinejad made a series of comments threatening Israel and proudly asserting the success Iran was having in developing space and ballistic missile technology.
It wasn’t until the 2015 nuclear deal, which happened after Mr Ahmadinejad was replaced as president by the incumbent Hassan Rouhani, that relations began to improve – albeit temporarily.
The Joint Comprehensive Plan of Action (JCPOA), signed by Iran, the US, the UK, Russia, China, Germany and the EU, paved the way for a relaxation of sanctions imposed on Iran in return for the Iranian government ensuring its nuclear programme would be “exclusively peaceful”.
For a period of time diplomatic relations improved, with Iran providing evidence it was according with the deal’s terms and its co-signatories allowing trade to increase.
But in 2018, US president Donald Trump announced he was abandoning the agreement because it did not address some key American concerns.
He said it did not restrict Iran’s ballistic missile programme nor its support for militia in Iraq, Lebanon, Syria and Yemen, which Washington sees as destabilising to the Middle East.
Since becoming president in 2017, Mr Trump has shown a greater willingness than his predecessors to ally himself with Israeli Prime Minister Benjamin Netanyahu and his robust approach – and also to seek stronger alliances with Arab nations that were hostile to Iran, such as Saudi Arabia.
Mr Netanyahu, who has repeatedly warned about what he sees as an Iranian threat, presented in 2019 what he said was evidence of a previously undisclosed Iranian nuclear weapons facility and said he was telling “the tyrants of Tehran… Israel knows what you are doing”.
It has long been rumoured that Israeli agents operate in Iran, despite Israelis being banned from the country.
In 2012, after four other Iranian nuclear scientists were assassinated, a man accused of killing a Tehran physics professor admitted at his trial – before he was hanged – that he travelled to Tel Aviv and was trained by Mossad, the Israeli intelligence service.
In 2020, The New York Times reported that a US intelligence source had told it that Israeli agents assassinated Al Qaeda’s second-in-command inside Iran.
In recent months, there has been growing cooperation between Israel and several countries it previously regarded as enemies – after a thaw in relations with the United Arab Emirates, Bahrain, and even, potentially, Saudi Arabia, was brokered by the US under the Trump administration.
With the election to the US presidency of Joe Biden, who has asserted his support for the 2015 JCPOA, Israel’s government has expressed concern about showing warmth towards Iran. Last week, Mr Netanyahu said there should be no return to the deal.
Iran has blamed Israel for the assassination of one of Iran’s most prominent nuclear scientists, Mohsen Fakhrizadeh, but there has been no comment so far from Mr Netanyahu.