On Sunday, the Tehran-backed Houthi guerrillas, who have managed to control much of Yemen, attacked an American warship and three British commercial vessels in the Red Sea. This comes on the heels of a series of maritime attacks on targets loosely connected to Israel and the U.S., documented in the article below by Mark Dubowitz and Richard Goldberg. They explain that Washington must respond far more forcefully than it has been:

President Biden refuses to add the Houthis back to the official U.S. terror list—a status he revoked shortly after taking office. And [Iran’s Supreme Leader Ali] Khamenei keeps driving toward a weapon of mass destruction with the UN’s nuclear watchdog warning that Iran is increasing its production of high-enriched uranium while stonewalling inspectors.

Refreezing all cash made available to Iran over the last few months and cracking down on Iranian oil shipments to China are the easy first steps. Senators can force Biden’s hand on both counts by voting on two bills that passed the House with overwhelming bipartisan support.

Next comes the reestablishment of U.S. military deterrence. America must defend itself and regional allies against any attempt by Iran to retaliate—a reassurance Riyadh and Abu Dhabi [also] need, given the potential for Tehran to break its de-escalation pact with the Gulf Arab states. By striking Iranian and Houthi targets, Biden would advance the cause of Middle East peace.  . . . Tehran will keep attacking Americans and U.S. allies unless and until he flashes American steel.

When the IDF finally caught up with the late Hamas leader Yahya Sinwar, he wasn’t deep inside a subterranean lair, as many had expected, but moving around the streets the Rafah. Israeli forces had driven him out of whatever tunnel he had been hiding in and he could only get to another tunnel via the surface. Likewise, Israel hasn’t returned to fight in northern Gaza because its previous operations failed, but because of its success in forcing Hamas out of the tunnels and onto the surface, where the IDF can attack it more easily. Thus maps of the progress of the fighting show only half the story, not accounting for the simultaneous battle belowground.

At the beginning of the war, various options were floated in the press and by military and political leaders about how to deal with the problem posed by the tunnels: destroying them from the air, cutting off electricity and supplies so that they became uninhabitable, flooding them, and even creating offensive tunnels from which to burrow into them. These tactics proved impracticable or insufficient, but the IDF eventually developed methods that worked.

John Spencer, America’s leading expert on urban warfare, explains how. First, he notes the unprecedented size and complexity of the underground network, which served both a strategic and tactical purpose:

The Hamas underground network, often called the “Gaza metro,” includes between 350 and 450 miles of tunnels and bunkers at depths ranging from just beneath apartment complexes, mosques, schools, hospitals, and other civilian structures to over 200 feet underground. . . . The tunnels gave Hamas the ability to control the initiative of most battles in Gaza.

One elite unit, commanded by Brigadier-General Dan Goldfus, led the way in devising countermeasures:

General Goldfus developed a plan to enter Hamas’s tunnels without Hamas knowing his soldiers were there. . . . General Goldfus’s division headquarters refined the ability to control forces moving underground with the tempo of the surface forces. Incrementally, the division refined its tactics to the point its soldiers were conducting raids with separate brigades attacking on the surface while more than one subterranean force maneuvered on the same enemy underground. . . . They had turned tunnels from obstacles controlled by the defending enemy into maneuver corridors for the attacker.

This operational approach, Spencer explains, is “unlike that of any other military in modern history.” Later, Goldfus’s division was moved north to take on the hundreds of miles of tunnels built by Hizballah. The U.S. will have much to learn from these exploits, as China, Iran, and North Korea have all developed underground defenses of their own.