The Saudi Arabia-led regional coalition continued to pound Houthi targets in Yemen over the weekend and on Monday. The most recent target of this Arab coalition’s air power was apparently an arms depot in the Yemeni capital of Sanaa.

This video of the blast taken by Yemen watcher Hisham al-Omeisy reveal the staggering scope of the blast:

More raw video of this attack via the regional news source Khabar Agency provides a better view of the initial blast and the series of secondary explosions that indicate an arms depot had been hit.

As the United States has come to learn, an air war without a ground component quickly begins to yield diminishing returns. The Saudis and Egyptians, as well as the eight other members of the primarily Sunni coalition of nations, know this and they are not prepared to limit their campaign against this Iranian proxy in Yemen to airstrikes. According to reporting, a ground invasion at the invitation of what the White House considers the legitimate Yemeni government can be expected shortly.

Saudi Arabia and Egypt have both talked about the possibility of putting boots on the ground. On Saturday, Yemeni Foreign Minister Riyadh Yaseen said he expected coalition troops to be in Yemen within days.

Saudi leaders have said that if troops do go in, they won’t leave until they have degraded the Houthis’ ability to fight. The Houthis are apt guerrillas. A fight on the ground could prove bloody and lengthy.

Hours ago, reports of columns of Saudi military hardware heading south toward the Yemeni border indicated that an invasion of Yemeni territory was not merely likely but imminent.

CNN is not the only news outlet to warn that the Saudi-led coalition forces could encounter a debilitating fight if they mounted a conventional invasion of Yemen. Moreover, the chaos in Yemen could prove a boon to terrorist elements like al-Qaeda in the Arabian Peninsula. “A protracted conflict in Yemen could also empower Sunni extremists in the impoverished and deeply tribal country,” the AFP reported.

Even with a variety of obstacles before the coalition of nations fighting Iranian influence in Yemen, the perceived necessity of the campaign is driving the engagement. Reportedly, the coalition of Iran opponents is about to get larger by one major, nuclear-armed player: Pakistan.

Largely Sunni Muslim Pakistan – a regional ally of Saudi Arabia, the Gulf’s main Sunni Muslim power – would join a Saudi-led military coalition conducting air strikes against Shi’ite Houthi forces, the official said.

The air strikes are targeting the rebels’ southward advance on the port city of Aden, the last bastion of Saudi-backed president, Abd-Rabbu Mansour Hadi.

Pakistan’s Defence Minister Khawaj Asif denied that the country had made a decision to send troops to Saudi Arabia, saying a delegation led by him and foreign policy chief Sartaj Aziz, would go to Saudi Arabia on Tuesday and then decide.

With a new war in the Middle East almost certain to expand in scope, it’s unclear how much control the White House has over the actors in this campaign. What’s more, the administration’s present ability to defend U.S. interests in the region is equally debatable.