American diplomats in recent decades have helped bring about an Israel-Egypt peace treaty, the peaceful fall of the Soviet Union, the unification of Germany, the end of the Bosnia war and a deal to curb Iran’s nuclear program. That record testifies to the power and influence of America as well as the skill of secretaries of state and other diplomats who worked to advance international stability and the national interest.

That isn’t the way the Trump administration approaches the world. Rex Tillerson is widely seen as ill suited to diplomatic leadership and determined to dismantle his own department, which has been central to America’s national security since Thomas Jefferson ran the place. The department is being undermined by budget cuts, a failure to fill top jobs, an erratic president and a secretary who has called reorganization, rather than policy, his most important priority. Given the aggressive behavior of North Korea, Russia and China in a world that seems shakier by the day, the timing could hardly be worse.

Meanwhile, the Pentagon is going gangbusters. The State Department’s budget has been targeted with a 31 percent cut, to $37.6 billion, but Congress is moving to raise the Pentagon’s spending level roughly 15 percent from the $549 billion allowed under the Budget Control Act. Aircraft carriers and tanks are obviously much more expensive than diplomatic pouches and airline tickets. Even so, such lopsided budget priorities could favor military solutions over diplomacy and development.

In recent weeks, alarming new data from the American Foreign Service Association, the union representing diplomats, shows just how far Mr. Tillerson has taken things. Since January, more than 100 senior foreign service officers have left the department, depleting the ranks of career ambassadors, the diplomatic equivalent of four-star generals, by 60 percent, while the number of career ministers (akin to three-star generals) is down 42 percent. The hiring of new foreign service officers has slowed almost to a halt, and the number of young people seeking to take the foreign service exam has fallen to less than half the 17,000 who registered two years ago.