In the weeks since an American drone strike killed Iranian Maj. Gen. Qasem Soleimani, U.S. military leaders have been sprinting to confront a dangerous new reality in the Middle East. From Saudi Arabia, where troops are setting up the first U.S. presence in more than a decade; to Syria, where small teams of Americans operate near Iranian-linked forces; to Afghanistan, where officials have detected an increase in Iranian aid to the Taliban, the military is bracing for a potentially catastrophic escalation. In visits to seven countries over the past six weeks, the top U.S. commander for the region, Gen. Kenneth "Frank" McKenzie Jr., cautioned American troops that the ballistic missile strike Iran launched days after Soleimani's death in Baghdad on Jan. 3 was unlikely the final salvo following Iran's loss of a peerless military figure. "They're under greater pressure, and entities under great pressure can react very aggressively," McKenzie told sailors in the Arabian Sea. Officials say Iran and its proxies have used rockets and mortars in a resumption of smaller-scale attacks on U.S. and allied targets since Soleimani's death and, in a previously unreported development, what American officials believe was a modified Russian SA-6 surface-to-air missile to shoot down a Saudi aircraft over Yemen on Feb. 14. Saudi officials earlier this past week also announced they had disrupted an attempted attack on an oil tanker off Yemen using remote-controlled explosive boats, recalling earlier incidents the kingdom has blamed on Iranian-linked Houthi rebels. What Iran's long-term response will be, and how President Trump might answer, are some of the unknowns military leaders must contend with in the months ahead. A possible acceleration of Iran's long effort to end the U.S. presence in the Middle East is one reason military leaders are racing to put new protections in place for American troops, now seen at greater risk, as they watch for signs of changed Iranian behavior. Soleimani’s death “was such a shock, so outrageous and such a break from past American behavior that Iran has basically decided it needs the U.S. out, and needs them out in real time,” said Kenneth Pollack, a scholar at the American Enterprise Institute. “It’s just too dangerous for Iran to live next door to Donald Trump.” About 80,000 U.S. service members are deployed across the U.S. Central Command’s area of control, 20,000 more than when U.S. officials say a string of Iranian provocations against the United States and its allies began last spring. The Pentagon has placed additional missile defense systems in countries including Saudi Arabia and Jordan over the past year. But the exposed nature of many U.S. outposts was made clear on Jan. 8, when Tehran launched about a dozen ballistic missiles at two bases housing U.S. troops in Iraq, the first such attack on American forces since the 1991 Persian Gulf War. U.S. commanders credited advance warning systems — along with a healthy dose of luck — for the bloodless outcome, though more than 100 service members suffered concussive injuries. McKenzie traveled to Iraq in early February to get a firsthand look at the wreckage at the Ain al-Asad base, where charred sleeping quarters and giant impact craters were proof of the challenges military leaders must confront. The Marine general brought years of combat experience in America’s post-2001 counterinsurgency wars — including deployments to Iraq and Afghanistan — to Centcom when he assumed command last spring. W.P