In the weeks since Russia invaded Ukraine, tensions between the world’s two biggest nuclear-armed powers have reached Cold War levels of brinksmanship. The shocking video of a Russian jet buzzing and apparently downing a US drone over the Black Sea has triggered angry rhetoric and even talk of a new arms race. But a direct military confrontation is unlikely, experts say.

A military confrontation could exacerbate political polarization and hurt President Obama’s chances for reelection. The White House has warned that it will retaliate for any Russian attack on the United States, but it has not said what that would mean. The escalating crisis also has revived Republican presidential candidates’ efforts to use national security issues to portray Mr. Obama as weak and ineffectual.

Russia has lined thousands of troops, tanks and artillery units along the Ukrainian border. And in September, the Kremlin ordered Russian citizens to enlist in the armed forces to support its invasion of Ukraine. The State Department has issued a travel advisory warning U.S. citizens to avoid all travel to Russia and warns that Russian security officials may arrest or single out U.S. citizens for detention, harass or other actions without adherence to internationally recognized legal standards.

With Russia ranking second in global military strength and the US ranked first, many worry that Russia could take over the Baltics and break NATO’s promise to respond to any attack on one member by allies with force. To understand why that is not likely, we looked at the two countries’ current military capability, as reported by the International Institute for Strategic Studies in its yearly report on “The Military Balance 2022.”