What the U.S. military is doing in response to Russian actions in Ukraine

The Pentagon detailed a new round of deployments to Eastern Europe on Tuesday in response to Russia’s latest actions against Ukraine, sending fighter jets, attack helicopters and infantry troops as it bolsters security in the region.

The deployments were announced as President Joe Biden also disclosed new sanctions aimed at punishing Russia, and they come on the heels of other similar moves by the Pentagon as the crisis has escalated. No U.S. troops will fight in Ukraine, Biden has said, but the crisis has prompted waves of American deployments from both the United States and U.S. installations in Europe.

“These additional personnel are being repositioned to reassure our NATO allies, deter any potential aggression against NATO member states, and train with host-nation forces,” the Pentagon said in a statement. “They will report to General Tod Wolters, Commander, U.S. European Command.”

Some noteworthy details to consider:

Why is the U.S. willing to deploy troops in Eastern Europe but not in Ukraine?

In short: Obligations.

In the aftermath of World War II, the United States, Canada and several allies in Western Europe established the North Atlantic Treaty Organization (NATO) to provide collective security against the Soviet Union. Among the alliance’s founding principals is that an attack on one NATO country is considered an attack on all, obligating NATO nations by treaty to stick together in a time of crisis.

NATO has expanded for years, from 12 nations in 1949 to 30 today, and has grown to include former Soviet republics such as Latvia, Estonia and Lithuania. That has riled Russian President Vladimir Putin. Other former Soviet states, notably Ukraine and Georgia, have sought membership, but their applications have languished in part because allowing them to join would require the rest of NATO to defend them against Russia.

Putin has sought guarantees that Ukraine will not break free from his sphere of influence more fully by joining NATO, and he has complained bitterly about NATO expansion. Resolution of the crisis now will likely require addressing the issue in some fashion.

How many U.S. troops are deployed in Europe and why?

Even in peacetime, the Pentagon’s presence across Europe is vast - a legacy, in part, of World War II. More than 90,000 U.S. troops are on the continent or sailing near it, with about 35,000 based in Germany alone.

The military relationships across the continent are driven in part by deals established in the liberal world order, a framework established after World War II that sought to prioritize peace, democracy and the rule of law across the globe, as well as counter the Soviet Union in the Cold War.

While the framework has required significant defense spending and deployments on the part of the United States, it also has provided U.S. bases in the region that have proven invaluable. One example: The majority of U.S. troops requiring emergency surgery after suffering injuries in Iraq or Afghanistan received treatment at a U.S. Army hospital in Landstuhl, Germany.

Other major U.S. troop concentrations in Europe are based in Italy, Britain and Spain. The United States has maintained close military ties with other nations, including some, such as Poland, that are close to Russia.

What has the Army done in recent days?

Among the first steps the U.S. military took was deploying several thousand soldiers with the 82nd Airborne Division at Fort Bragg, N.C., to Poland.

The soldiers did not deploy with tanks or other heavy weapons that would be needed to take on Russia in Ukraine. But they are a visible symbol of American presence, including near Przemysl, a Polish city just a few miles from the Ukrainian border.

Pentagon spokesman John Kirby has said the soldiers will not deploy inside Ukraine but could have a wide range of missions just across the border, including providing humanitarian assistance if waves of refugees fleeing bloodshed arrive.

The Pentagon also deployed a unit of about 1,000 soldiers operating Stryker armored combat vehicles this month from Germany to Romania, where they joined about 900 U.S. troops who already were there. A smaller company of soldiers, numbering more than 100, was deployed to Bulgaria.

The moves announced by the Pentagon on Tuesday escalate the kinds of weaponry arriving in the area. Among the soldiers involved are pilots flying AH-64 Apache gunship helicopters and their support crews, and about 800 paratroopers with the 173rd Airborne Brigade, who are based in Vicenza, Italy.

How are the other services involved?

While the bulk of U.S. military deployments announced so far in the crisis have been from the Army, each service in the Defense Department already is involved.

Notably, the Navy has kept the Harry S. Truman carrier strike group - a powerful formation of ships that includes an aircraft carrier named after the former president - in the region for weeks. As of Monday, the strike group was in the Ionian Sea, off the coasts of Greece and Italy, participating in a NATO training exercise that includes ships, aircraft and submarines, according to Navy statements.

The Navy also has been flying P-8A Poseidon surveillance planes - which specialize in hunting submarines - from Italy over the Mediterranean Sea. Russian fighter jets have intercepted them, in some cases at distances that the Pentagon identified as unsafe and unprofessional.

On Tuesday, the Pentagon said that up to eight F-35 fighter jets will deploy to Eastern Europe as part of expanding operations, adding the military’s most advanced aircraft to the puzzle. Other fighter jets and surveillance planes have been spotted flying over the region for days.

The Marine Corps’ role in the crisis has been more limited so far, but it includes a team of embassy security guards who were based in Kyiv, the Ukrainian capital, until the United States withdrew from the diplomatic compound last week. The United States had dispatched eight additional embassy guards to Kyiv to bolster security there before pulling out, Marine officials told reporters last month.

What might NATO do?

U.S. troops deployed in the crisis so far report to U.S. European Command, the geographic headquarters in Stuttgart, Germany, that oversees American operations across the continent. But NATO allies have increasingly stepped forward, too, sending weapons to Ukraine and troops to bolster forces in Eastern Europe.

There’s another major step that NATO can take, however. The alliance has at its disposal a multinational unit called the NATO Response Force that numbers about 40,000 troops. NATO has never activated the force, in part because doing so requires the consent of all 30 members of the alliance.

Since Russia’s 2014 invasion of Ukraine’s Crimean Peninsula and subsequent annexation of it, NATO has taken several other steps to bolster security. They include establishing a multinational brigade in Romania, an air policing mission, and a Very High Readiness Task Force, or VJTF, that is on alert to deploy at a moment’s notice.