Not since Yom Kippur in 1973 has the Middle East been so close to all out war.

That conflict, also known as the Ramadan War, raged for 19 days between Israel and a coalition of Arab states led by Egypt and Syria. It claimed up to 20,000 lives, including some 2,500 Israeli soldiers. Many thousands more on both sides were maimed and injured.

It is a reminder of what is at stake today after the biggest exchange of fire on the Israel-Lebanon border.

Exactly what happened in the early hours of Sunday morning remains obscured by the fog of war and the desperate need for both sides to establish deterrence through strength – real and perceived.

Israel says it moved first and pre-emptively after detecting Iranian-backed Hezbollah was poised to launch a major strike in revenge for the assassination of Fuad Shukr, one of its most senior commanders, in Beirut on July 31.

Rear-Adml Daniel Hagari, Israel’s military spokesman, said 100 Israeli jets had hit 40 sites in southern Lebanon, destroying thousands of rocket launchers that were primed for use against Israel.

Hezbollah said Israel’s defences had failed and implied that it had successfully hit 11 Israeli sites including a “special military target” in central Israel in an attack involving more than 320 Katyusha rockets and a “large number” of drones.

“The enemy’s claims about the pre-emptive action it carried out, the targets it struck and its disruption of the resistance’s [Hezbollah] attack are empty,” said the group in a statement.

The attack was just the “first phase” of its retribution for Israel’s killing of Shukr, it added, suggesting that may follow.

Whether or not the latest exchange can be contained is likely to be determined by the actions and diplomacy of the US and Iran.

Both say they want to avoid a regional war and both have considerable influence over the two sides but do not control them.

Lloyd Austin, the US defence secretary, called his Israeli counterpart Yoav Gallant on Sunday morning to stress “the importance of avoiding regional escalation”.

In response, Israel said it was not looking for a wider war but added that its “defence establishment is determined to defend the citizens of Israel and will use all the means at its disposal to remove imminent threats”.

Likewise Abbas Araghchi, Iran’s new foreign minister, called for dialogue to resolve bilateral issues in a call with the EU’s top diplomat on Thursday.

“In our foreign policy, it is our responsibility to minimise the costs of the [US] aggression to the greatest extent possible,” he said, indicating a desire in Terahn to lower tensions in the region.

Another positive – although a faint one – was that the Gaza ceasefire and hostage talks were continuing in Cairo on Sunday.

Hassan Nasrallah, Hezbollah’s leader in Lebanon, was set to address the latest developments in a televised speech at 4pm UK time on Sunday – perhaps providing greater clarity on the group’s intentions.

The hope will be that Nasrallah, who is close to Iran, claims success in Hezbollah’s overnight actions and stands down his fighters, saying that honour has been restored.

Whether or not that would be enough for Israel, only time will tell.

Since the start of the war on Oct 7, Israel has had to evacuate 60,000 to 80,000 people from an area of some 650 square kilometres along the Lebanon border – about 3 per cent of its total land mass – because of Hezbollah’s rockets.

Benjamin Netanyahu, Israel’s prime minister, said on Sunday: “We are determined to do everything to protect our country, return the residents of the north safely to their homes and continue to uphold a simple rule: whoever hurts us – we hurt them.”