Correction: Due to an editing error, James Jeffrey’s op-ed said that a ground deployment of U.S. troops “to Ukraine today could change perceptions on all sides.” The writer was referring to areas along Ukraine’s borders, and the column should have said that “a ground deployment in the current crisis with Russia could change perceptions on all sides.”

James Jeffrey is a distinguished visiting fellow at the Washington Institute for Near East Policy. He was U.S. ambassador to Iraq in the Obama administration and deputy chief of mission to Kuwait from 1996 to 1999.

Despite the deal Thursday in Geneva, the situation in Ukraine remains volatile. There was apparently no agreement that Russian President Vladi­mir Putin would pull back his troops massed near the Ukrainian border. Judging from Putin’s address to the Russian people while his foreign minister was negotiating with the United States, the European Union and Ukraine, he has not given up his goal of controlling much or even all of this strategically vital European country.

The West’s reaction has been weak at times. The sanctions imposed and contemplated are not dramatic, regardless of immediate Russian losses in volatile stock and currency exchange markets. Europe’s dependence on Russian hydrocarbons and affinity for Russian investments were apparent week when the German foreign minister feted Russian First Deputy Prime Minister Igor Shuvalov for trade talks, even as NATO photos of Russian military equipment stockpiled near Ukraine emerged. While European foot-dragging is the biggest obstacle to an effective response, some of Washington’s initial comments and actions suggested an unwillingness to face the reality of Putin’s actions. The Obama administration also bears the burden of its Middle East policy of avoiding military conflicts. NATO member states in Eastern Europe are asking the same question many in the Middle East have: Can we rely on Washington to make hard military decisions?

The best way to send Putin a tough message and possibly deflect a Russian campaign against more vulnerable NATO states is to back up our commitment to the sanctity of NATO territory with ground troops, the only military deployment that can make such commitments unequivocal. To its credit, the administration has dispatched fighter aircraft to Poland and the Baltic states to reinforce NATO fighter patrols and exercises. But these deployments, as with ships temporarily in the Black Sea, have inherent weaknesses as political signals. They cannot hold terrain — the ultimate arbiter of any military calculus — and can be easily withdrawn if trouble brews. Troops, even limited in number, send a much more powerful message. More difficult to rapidly withdraw once deployed, they can make the point that the United States is serious about defending NATO’s eastern borders.

While examples of effective ground force “tripwires” date to the U.S. brigade in Berlin during the Cold War, the most relevant recent example is Kuwait after 1993. To deter Saddam Hussein from any new attack, the United States maintained a “heavy brigade package” of armor and other materiel to equip a force of 5,000 troops to be quickly flown in if needed. The United States and Britain also maintained fighter aircraft in Kuwait. All this, however, was not sufficient to fully deter Hussein. U.S. ground forces were deployed in 1994, 1996 and 1997-98. Even with equipment already deployed, it took time to fly the troops in, and the decisions required precious time for Washington and the Kuwaiti government to deliberate.

To deal with these issues, the Clinton administration finally stationed a small ground force in Kuwait, rotated from stateside units on six-month deployments. In a crisis, the thinking went, it would buy time for a full brigade to deploy and encourage rapid Kuwaiti deployment, possibly deterring a ground attack. In Operation Desert Fox in December 1998, the United States went with the force on the ground, rapidly reinforced by a Marine expeditionary unit, rather than wait for a brigade to deploy and thus signal its intentions to Hussein.

If the Russians do not stop their destabilization of eastern Ukraine as they have agreed, and in particular do not stand down their conventional forces on the Ukrainian border, then the administration, after consulting with NATO, should inform Moscow that it will station limited forces in Poland, the Baltic states and Romania. Initial contingents could be as small as companies (150 soldiers) on “training” maneuvers, but equipment for larger forces and a permanent rotation of troops could be quickly organized. Although Russian ground forces near Ukraine number an estimated 40,000 or more, a small U.S. force could rally affected nations to commit their own larger forces and encourage other NATO states to deploy troops. Taken together, that would provide more than a tripwire, generating time for larger reinforcements and complicating any threat against NATO states or even Crimea-style intervention in Ukraine.

Would such a deployment be provocative? Only if being serious about deterring Putin is provocative. Would it violate “understandings” with Moscow eschewing such U.S. stationing? Probably, but Putin has already violated a library’s worth of understandings, agreements and treaties pertaining to territorial integrity. His actions undercut the basis for NATO defense thinking since 1991, but no U.S. or European response has delivered the West’s promised “serious consequences” and “different relationship” with Russia. Deploying troops would do so.

We do not need to be apologetic about the risk of even “tripwire” presences. Putin has no illusions about the United States’ combat-hardened conventional superiority. But, by all appearances, he has great doubt about U.S. willingness to use force, and that creates a dangerous situation. After seeing American boots on the ground, Hussein decided not to threaten Kuwait anew. But recall that half a world away and six decades ago, the United States took a different approach, withdrawing its forces from South Korea. North Korea and its Russian supporters saw that as a green light to invade, only to learn, three years and millions of casualties later, that the United States was serious about defending a friend.