For more than a decade, he was a feared presence in Iran, presiding over a vast intelligence apparatus. He crushed domestic dissent and political rivals and expanded covert operations beyond Iran’s borders to target dissidents and enemies abroad.

Hossein Taeb, a 59-year-old cleric and chief of intelligence for the powerful Islamic Revolutionary Guards Corps, seemed untouchable.

That was until he was abruptly removed from his position last week, a casualty of a relentless campaign by Israel to undermine Iran’s security by targeting its officials and military sites, according to officials and analysts in both countries.

A botched Iranian effort to target Israeli citizens in Turkey, which caused an embarrassing diplomatic crisis with Ankara, a regional ally of Tehran, eventually tipped the balance, according to Israeli intelligence officials briefed on the Iranian plot who requested anonymity to discuss sensitive operations and intelligence topics.

The removal of Mr. Taeb was an acknowledgment by Tehran that confronting the threat from Israel required new leadership and a reset of strategies and protocols, according to Mohammad Ali Abtahi, a reformist former vice president of Iran and cleric who was ousted by conservatives in 2009 but has maintained close ties to top officials.
“The security breaches inside Iran and the vast scope of operations by Israel have really undermined our most powerful intelligence organization,” Mr. Abtahi said by telephone from Tehran. “The strength of our security has always been the bedrock of the Islamic Republic and it has been damaged in the past year.”

Calls to purge Mr. Taeb appeared amid a growing climate of mistrust within the Iranian leadership after a senior commander in the Revolutionary Guards, Brig. Gen. Ali Nasiri, was secretly arrested on allegations of spying for Israel, according to a person with close ties to top officials in the Revolutionary Guards and another with knowledge of the arrest. They and other Iranian officials quoted in this article requested anonymity because they were not authorized to speak on the record about internal discussions.

Officials with Iran’s mission to the United Nations said they had no immediate comment about the claims.

General Nasiri’s detention came two months after several dozen employees of the Ministry of Defense’s missile development program were arrested on suspicion of leaking classified military information, including design blueprints of missiles, to Israel, according to an Iranian official familiar with the raid.

During the past year, Israel has intensified the scope and frequency of its attacks inside Iran, including on the nuclear and military sites that Mr. Taeb’s organization was responsible for protecting.

One of the Israeli officials said that part of the strategy entailed exposing failures by the Revolutionary Guards in their covert war with Israel in the hope that it would create conflict between political leaders and the defense and intelligence establishment.

On Monday, three Iranian steel factories, one of them the state-owned Khuzestan Steel, were hit in a cyber attack forcing one to halt its production line. The three factories hit Monday are major suppliers of steel to the Revolutionary Guards, according to a Western intelligence official.

A group of hackers known as Gonjeshke Darande claimed responsibility. The same group claimed responsibility for another cyber attack in November that disabled gas stations across Iran and that U.S. officials said was connected to Israel. Officials in Israel declined to confirm the source of the attacks.

Israel’s spy network has infiltrated deep into the rank and file of Iran’s security circles, Iranian officials have acknowledged, with Iran’s former minister of intelligence warning last year that officials should fear for their lives, according to Iranian media reports.

Keren Hajioff, a senior adviser to Prime Minister Naftali Bennett of Israel, said in an interview that the strategy targeting Iran was part of Mr. Bennett’s “octopus” doctrine.

“This doctrine is a strategic shift from the past, when Israel focused on Iran’s proxy ‘tentacles’ across the region, in Lebanon, Syria and Gaza,” she said. The new tactic, she added, was “a paradigm shift: Now we go straight for the head.”

Israeli agents have carried out assassinations with remote-controlled robots and in drive-by shootings, flown drones into sensitive missile and nuclear facilities, and kidnapped and interrogated an agent of the Revolutionary Guards inside Iran. Tehran also suspects that Israel killed two of its scientists in May.

Mr. Taeb was appointed the head of the Revolutionary Guards’ intelligence organization in 2009 after nationwide unrest over disputed presidential elections. He had previously served as the chief of the Basij, a plainclothes militia notorious for attacking and sometimes killing protesters.

Mr. Taeb enforced systematic crackdowns with a brutality that elevated the intelligence organization from an obscure security unit to the most feared spying operation in the country.

Mr. Taeb, a trusted ally of Iran’s supreme leader, Ayatollah Ali Khamenei, placed opposition leaders under house arrest, dismantled many civil society groups, arrested activists and dual nationals and kidnapped dissidents in neighboring countries. In at least one incident, one of the dissidents was executed after being forcibly returned to Iran. In a video praising Mr. Taeb released by the Revolutionary Guards this week, those actions were cited among other “accomplishments.”