On Thursday, Sweden, rattled by a combination of Russian aggression in eastern Europe and Donald Trump’s tepid support for NATO during the presidential campaign, reinstated the draft. Conscription had been abolished in 2010, after decades of Sweden being content to let NATO, of which it is not a member, stand against possible Russian expansionism.

But now four thousand men and women will be drafted to join the volunteer defense force already in place.

As The New York Times reports, at the end of 2016, the Swedish Civil Contingencies Agency sent a letter warning municipalities around the country that the country needed to “increase their ability to resist an armed attack against Sweden from a qualified opponent.”

Christer Stoltz, chief of contingency planning for Gotland, Sweden’s largest island, admitted, “For two decades, our contingency planning was low. Now, we need to look at our plans.”

Henrik Breitenbauch, the director of the Center for Military Studies in Copenhagen, explained, “The threat of the U.S. no longer wanting to honor its security guarantees is the most important development in the history of the alliance. It has created high levels of concern all over Europe.”

Peter Hultqvist, Sweden’s defense minister, added that Europe had been too sanguine about any Russian aggression after the Cold War, saying, “Politicians at the time maybe thought that the future would be more sunny than the reality is today. From my point of view, many mistakes have been made over the years. The security situation and what could come in the future was underestimated.”

He had a point; Sweden’s military spending dropped from 2.6% of G.D.P. in 1991 to 1.1% in 2015. But after Russia annexed Crimea and became involved in Ukraine, Swedish military spending rose 11%.

Gotland, in particular, feels threatened, as it is close to Kaliningrad, a Russian outpost. As The Daily Wire reported last October, “The Russians are also moving Iskander missiles to Kaliningrad, a Russian territorial outpost south of Lithuania, north of Poland, and within striking distance of the rest of the Baltic states. Putin promised this wouldn’t happen after Obama withdrew missile defense from Poland.”

Marinette Radebo, a spokeswoman for the Defense Ministry, asserted, “We see a lot of activity in the Baltics and a lot of training, provocative flights and military exercise going on in our neighborhood.”

In the Journal of Strategic Studies, a study found Russia was using “active measures” toward Sweden, such as forged documents, disinformation, military threats and agents of influence.

In May, all Swedish municipalities will participate in a “Contingency Week,” teaching Swedes how to prepare for 72 hours in case of an emergency.