LONDON – Iran's immediate response to Israel's strike on Dahiyeh, Hezbollah's stronghold in Beirut, came as a surprise to many observers. Through this action, Iran established a new deterrence equation in West Asia. The Israeli side subsequently sought to test the credibility of this equation through limited provocations, effectively "testing the waters" of Iran's declared policy.

For the first time in the history of the Islamic Revolution, Iran intervened directly in response to military strikes against its allies. This new doctrine holds that any aggression against Iran or its allies, or any violation of agreements involving them, will trigger an immediate response from Iran proportional to the scale of the aggression or breach.

The objective of the Israeli military operation in Beirut's southern suburbs was to test the credibility of Iran's new deterrence doctrine. Many believed that Iran would refrain from responding, as it had during an earlier phase. This assumption was rooted in the expectation of continuity—that Iran would maintain the same posture of strategic patience it had previously adopted to allow for preparation and readiness.

This occurred at a time when Israel had not yet displayed the degree of its brutality that later became a defining characteristic of its conduct following the October 7 incident.

After October 7, Israel appeared to operate under the assumption that it could dismantle the Axis of Resistance and eventually strike at its backbone in Iran. Following a series of Israeli actions—including the attack on Iran's consulate in Damascus, the assassination of Hamas leader Ismail Haniyeh in Tehran, and, most significantly, the assassination of Hezbollah Secretary-General Sayyed Hassan Nasrallah in Beirut—Tehran concluded that Israel's escalation had reached unprecedented levels and that a punitive response had become necessary.

When Donald Trump returned to the White House, Benjamin Netanyahu appeared to believe that the time had come to settle scores with Tehran. In June 2025, Israel launched a surprise war against Iran with U.S. backing and direct Pentagon involvement. Iran's response forced Israel to seek a ceasefire.

However, on February 28, Israel and the United States jointly attacked Iran, apparently believing that such an operation could destabilize or even topple the Islamic Republic. The attack proved costly for Washington and Tel Aviv. Iran responded by taking the drastic step of closing the strategic Strait of Hormuz, through which roughly a quarter of the world's oil and gas supplies pass.

After punishing Israel and humiliating the United States, Iran agreed to a conditional ceasefire on April 8. The agreement included all fronts, including a cessation of Israel's military operations in Lebanon. Yet Israel sought to manipulate the ceasefire by violating its terms.

Israeli leaders continued military operations in Lebanon while testing the credibility of Iran's warnings. They appeared to calculate that if violations went unanswered, further breaches could be undertaken and later presented as strategic achievements.

However, Iran reinforced its new deterrence equation by demonstrating that every violation would be met with an immediate response.

Likewise, what Tehran viewed as partial incursions against Iranian islands near the Strait of Hormuz were met with swift retaliation, reinforcing the message that both Israel and its principal ally, the United States, were confronted with a new reality on the ground.

Another assumption held by Israel and its allies was that Iran would not jeopardize its own security for the sake of its allies. According to this line of thinking, if Iran failed to respond, further military pressure could be applied, particularly against Hezbollah, Tehran's closest ally in Lebanon.

Israeli leaders also sought to promote the perception that Iran was abandoning its allies. The objective was to weaken confidence in Tehran among resistance movements and regional partners.

The new equation established by Iran has altered the rules of the game. Israel has come to realize that Tehran is serious about defending its allies and that any breach of agreements or escalation on any front is likely to provoke a response.