State media confirmed on Monday that President Ebrahim Raisi, as the head of the Supreme National Security Council (SNSC), has appointed Ali Akbar Ahmadian, a senior commander in the Islamic Revolutionary Guard Corps (IRGC), as Shamkhani’s replacement.

Shamkhani had been appointed as the secretary of the SNSC in September 2013 and has been instrumental in shaping the Islamic Republic’s security policies in the past decade.

He appeared to announce his departure late Sunday by posting an excerpt of a cryptic poem on Twitter from 16-century Iranian poet Muhtasham Kashani.

Shamkhani leaves his post after having successfully completed a detente with Saudi Arabia, which saw the two countries agree to restore diplomatic ties after a seven-year rift in a China-brokered deal in March.

Tehran is also on track to improve its diplomatic relations with other neighbours across the region while also increasingly cosying up to Russia and China, as its ally Syria has also been welcomed back into the Arab League.

Relations with the West, however, remain highly confrontational, amid stalled efforts to restore Iran’s 2015 nuclear deal with world powers and after protests rocked Iran last September. The SNSC had been in charge of the nuclear file, while also being one of the main entities managing the local unrest, but Shamkhani was only one of the voices at the council.

At an address on national security that turned out to be his farewell speech, Shamkhani said the world order is changing and the Islamic Republic needs to adapt its macro policies to it.

“A new world order at first would mean a disruption of the current order and disorder on the back of the evolution of the current order, but this is not inherently positive, and our readiness and role in the new world order is what can make its changes positive for us,” he said.

He also discussed the so-called “axis of resistance” of forces that are supported by Iran across the region, saying: “The current circumstances can turn out to be in favour of the axis of resistance, but we must not turn the doctrine of resistance into a doctrine of domination.”

In a meeting last week with Foreign Minister Hossein Amirabdollahian and Iran’s ambassadors in other countries, Supreme Leader Ayatollah Ali Khamenei also alluded to a changing world order, saying it will be a “rough process filled with unexpected events” that Iran needs to gear up for.

Why did he leave?

No detailed official reason has been given for Shamkhani’s departure, but it may indicate the country is heading in an ever-more conservative direction as Shamkhani was regarded as relatively pragmatic.

Shamkhani’s departure had been rumoured – and vehemently denied by state media – several times before, most recently earlier this year.

Speculations about his immediate departure had been rampant in January, after one of his former closest allies, dual national ex-official Alireza Akbari, was executed for spying for the United Kingdom.

The Iranian-British Akbari, who was one of Shamkhani’s deputies at the defence ministry 20 years ago, was hanged amid condemnations by the UK for allegedly acting as a “key spy” for the British intelligence service.

Shamkhani was also the second longest-serving security chief since the country’s 1979 revolution, which birthed the current theocratic establishment, behind only former President Hassan Rouhani who was SNSC secretary for nearly 16 years starting 1989.

It remains unclear how relevant he will remain in Iran’s power centres moving forward, but he has displayed he is adept at navigating the country’s military and political landscape during the past decades.

A man of versatility

Shamkhani, arguably the highest-ranking ethnic Arab figure within the establishment since the revolution, is the only top figure to have served at the highest levels of both the country’s army and the IRGC, and he has also held senior roles in reformist, centrist and conservative presidential administrations.

A career military man, he was one of the most influential figures in the IRGC during its nascent years following the revolution, and counted among its senior commanders during the eight-year Iran-Iraq War in the 1980s.

He led the elite force’s division in western Khuzestan province, which bore the brunt of the war, and was later promoted to deputy commander-in-chief, and then the head of IRGC ground forces.

Shortly after the war ended, Khamenei, who had just become the country’s supreme leader, appointed Shamkhani as the commander of the Iranian army’s navy, and later installed him as the IRGC navy chief. He currently holds the rank of rear admiral, the highest navy rank that the commander-in-chief of the armed forces – the supreme leader – can bestow.

When reformist politician Mohammad Khatami became president in 1997, Shamkhani was selected as his defence minister and held that post until 2001. Shamkhani challenged Khatami during the next election cycle, but failed to upset his re-election. He nevertheless returned as defence minister and served until 2005.

During the eight-year tenure of ultraconservative President Mahmoud Ahmadinejad, Shamkhani was largely away from the spotlight but made a comeback when moderate Rouhani won the presidency in 2013.

Rouhani, who as president led the SNSC, appointed Shamkhani as the secretary, replacing ultraconservative Saeed Jalili – who still plays a major role at the council as the supreme leader’s representative, and continues to influence Iranian domestic and foreign policy.

Shamkhani was Iran’s fourth security chief since the revolution after Rouhani, Ali Larijani, who was secretary for only about two years, and Jalili, who held the post for approximately six years.