Conflict has spread across the Middle East since Hamas’s surprise attack on Israel in October and Israel’s fierce counterattack in the Gaza Strip. From Lebanon to Iraq to the Red Sea, the violence all but amounts to an undeclared regional war pitting Iran-backed militant groups against Israel and the U.S. Israel is effectively fighting active battles on three fronts.

Gaza and the West Bank

The Israeli military campaign has downshifted in and around Gaza City after a ground invasion and air campaign flattened much of the strip’s north. But intense fighting continues in the south, where Hamas’s top leaders are suspected to be hiding out in tunnels with kidnapped Israeli hostages. Meanwhile, the Israeli military is conducting near-daily raids across the West Bank in what it says are operations to root out suspected terrorists. The operations have used air and drone strikes, which were once rare in the West Bank.

Lebanon-Israel Border

There are daily exchanges between the Israeli military and Iran-backed Lebanese militia group Hezbollah, a U.S.-designated terrorist group that has vowed to keep firing on Israeli positions for the duration of the war in Gaza. Israel, for its part, says it wants Hezbollah to pull its forces back from the border. Israel says it would prefer diplomacy but is prepared for war.

Red Sea

Iran-backed Houthis have conducted strikes targeting more than two dozen ships in the Red Sea and Gulf of Aden, upending ship traffic heading to and from the Suez Canal. In response, the U.S. has led dozens of strikes on Yemen in recent weeks.

Iran

The terrorist group ISIS-K struck an Iranian mourning ceremony for Gen. Qassem Soleimani, who was killed in a U.S. strike in 2020. Iran subsequently fired long-range missiles targeting what it said were terrorists in Syria, Iraq and Pakistan. Analysts said Iran was demonstrating its weapons’ capabilities to the world, and to the U.S. and Israel in particular. In turn, Pakistan fired back on Iran but was careful to say it didn’t want escalation.

Iraq

Iran-backed militias have fired dozens of rockets at American bases in Iraq and Syria. In response, the U.S. carried out a strike that killed a top Iraqi militia commander. Iraq now says that it is reconsidering hosting international troops.

Write to Carl Churchill at carl.churchill@wsj.com, Emma Brown at Emma.Brown@wsj.com and Michael Amon at michael.amon@wsj.com