In the last week alone, Israel has killed a senior Hamas militant in an airstrike in Beirut, Hezbollah has fired barrages of rockets into Israel, the US has killed a militia commander in Baghdad and Iran-backed rebels in Yemen have traded fire with the American Navy.

Each strike and counterstrike increases the risk of the already catastrophic war in Gaza spilling across the region. And in the decades-old standoff pitting the US and Israel against Iran and allied militant groups, any one party could choose all-out war over a loss of face.

The divisions within each camp add another layer of volatility: Hamas might have hoped its October 7 attack would drag its allies into a wider war with Israel. Israelis increasingly talk about the need to change the equation in Lebanon, even as the US aims to contain the conflict.

As the intertwined chess games grow ever more complicated, the potential for miscalculation rises.

Hamas says the October 7 attack that triggered the war in Gaza was an act of purely Palestinian resistance to Israel’s decades-long domination of the Palestinians. There is no evidence that Iran, Hezbollah or other allied groups played a direct role or even knew about it beforehand.

But when Israel responded by launching one of the 21st century’s most devastating military campaigns in Gaza, a besieged enclave home to 2.3 million Palestinians, the so-called Axis of Resistance – Iran and the militant groups it supports across the region – could hardly stay on the sidelines.

The Palestinian cause has deep resonance across the region, and leaving Hamas alone to face Israel’s fury would have risked unraveling a military alliance that Iran has been building up since the 1979 Islamic Revolution put it on a collision course with the West.

“They don’t want war, but at the same they don’t want to let the Israelis keep striking without retaliation,” said Qassim Qassir, a Lebanese expert on Hezbollah.

“Something big has to happen, without going to war, so that the Israelis and Americans are convinced that there is no way forward,” he said.

Of all Iran’s regional proxies, Hezbollah faces the biggest dilemma.

If it tolerates Israeli attacks, like the strike in Beirut that killed Hamas’ deputy political leader, it risks appearing to be a weak or unreliable ally. But if it triggers an all-out war, Israel has threatened to wreak massive destruction on Lebanon, which is already mired in a severe economic crisis. Even Hezbollah’s supporters may see that as too heavy a price to pay for a Palestinian ally.

Hezbollah has carried out strikes along the border nearly every day since the war in Gaza broke out, with the apparent aim of tying down some Israeli troops. Israel has returned fire, but each side appears to be carefully calibrating its actions to limit the intensity.

A Hezbollah barrage of at least 40 rockets fired at an Israeli military base on Saturday sent a message without starting a war. Would 80 have been a step too far? What if someone had been killed? How many casualties would warrant a full-blown offensive? The grim math provides no clear answers.

And in the end, it might not be a single strike that does it.

Israel is determined to see tens of thousands of its citizens return to communities near the border with Lebanon that were evacuated under Hezbollah fire nearly three months ago, and after October 7 it may no longer be able to tolerate an armed Hezbollah presence just on the other side of the frontier.

Israeli leaders have repeatedly threatened to use military force if Hezbollah does not respect a 2006 UN cease-fire that ordered the militant group to withdraw from the border.

“Neither side wants a war, but the two sides believe it is inevitable,” said Yoel Guzansky, a senior researcher at Israel’s Institute for National Security Studies at Tel Aviv University. “Everybody in Israel thinks it’s just a matter of time until we need to change the reality” so that people can return to their homes, he said.

The US positioned two aircraft carrier strike groups in the region in October. One is returning home but being replaced by other warships. The deployments sent an unmistakable warning to Iran and its allies against widening the conflict, but not all of them seem to have gotten the message.

Iran-backed militant groups in Syria and Iraq have launched dozens of rocket attacks on US bases. The Iran-backed Houthi rebels in Yemen have attacked international shipping in the Red Sea, with potential consequences for the world economy. Iran says its allies act on their own and not on orders from Tehran.

The last thing most Americans want after two decades of costly campaigns in Iraq and Afghanistan is another war in the Middle East. But in recent weeks, US forces have killed a senior Iran-backed militia commander in Iraq and 10 Houthi rebels who were trying to board a container ship, spilling blood that could call out for a response.

Washington has struggled to cobble together a multi-national security force to protect Red Sea shipping. But it appears hesitant to attack the Houthis on land when they appear close to reaching a peace deal with Saudi Arabia after years of war.

Israeli officials have meanwhile said the window for its allies to get both Hezbollah and the Houthis to stand down is closing. The regional tensions are likely to remain high as long as Israel keeps up its offensive in Gaza, which it says is aimed at crushing Hamas. Many wonder if that’s even possible, given the group’s deep roots in Palestinian society, and Israel’s own leaders say it will take many more months.

The US, which has provided crucial military and diplomatic support for Israel’s offensive, is widely seen as the only power capable of ending it. Iran’s allies seem to believe Washington will step in if its own costs get too high – hence the attacks on US bases and international shipping.

US Secretary of State Antony Blinken, the European Union’s top diplomat, Josep Borrell and German Foreign Minister Annalena Baerbock are all back in the region this week, with the aim of trying to contain the violence through diplomacy.

But the most important messages will still likely be sent by rocket.

“The Americans do not want an open war with Iran, and the Iranians do not want an open war with the United States,” said Ali Hamadeh, an analyst who writes for Lebanon’s An-Nahar newspaper. “Therefore, there are negotiations by fire.”

• An AP report