Army Secretary Mark Esper won plaudits on Capitol Hill for his laser focus on modernizing the US ground force for future conflicts with Russia and China. But he will have little time to hit the briefing books to deal with an escalating crisis with Iran as he takes over as the Pentagon’s acting secretary next week.

After the Defense Department called out Iran for shooting down an American surveillance drone over international waters on Wednesday, the newly-minted placeholder will ship out early next week to Brussels, where he will be charged with quickly rounding up NATO ministers to help build an international coalition to deter Iranian aggression.

"Not everybody is going to be Jim Mattis but you don’t have to be,” said Barbara Leaf, a former US ambassador to the United Arab Emirates. “Can he do it? I just don’t know. It’s such a steep learning curve, and he’s being thrown right into the deep end with this set of issues coming from Iran. It’s not going to end with this latest attack.”

In the latest escalation, Air Force Lt. Gen. Joseph Guastella said an Islamic Revolutionary Guard Corps surface-to-air missile struck a US Navy RQ-4 Global Hawk drone Wednesday night in an “an attempt to disrupt our ability to monitor the area,” insisting the US aircraft had not violated Iranian airspace. President Donald Trump said Iran made a “very foolish move” but indicated the strike was unintentional.