What are the best US military options for Ukraine?

Since last April, Russia has been slowly and methodically building up military forces near Ukraine’s border. Those who recall the 1990 U.S. military buildup in advance of the January “Desert Storm” attack to free Kuwait and invade Iraq, will recognize that such a buildup is a serious threat.  

But, as retired Foreign Area Officer Col. Jeff Hartman notes, those trying to predict when an invasion of Ukraine will occur have missed the fact that it already happened. It began in 2014 with the annexation of Crimea and the creation of a separatist region in Ukraine’s east.  Whatever comes next is only a continuation of that operation.  

Russia has been consistent in its messaging about Ukraine — namely, that Ukraine must remain a buffer between Russia and the West, outside NATO. To accomplish this goal, Russian President Vladimir Putin, as commander in chief, can still choose not to use military force in Ukraine, but he has unquestionably given himself military options to choose from. A major military operation in Ukraine would take most of Russia’s active military ground and airborne forces to accomplish, but it could be done.  

If the U.S. and West hope to prevent an armed conflict, and not just react to one, we can still take preventive steps now.  What are the options for the U.S. (and the West) to prevent Russia from “continuing” its invasion of Ukraine? They are complicated, for sure, and involve diplomatic, informational, military and economic actions. I will focus on military options, which could cause Russia to recalculate its chances of success in Ukraine. 

President Biden has said that putting American troops “on the ground” in Ukraine is “not on the table.” It is clear to most observers that the U.S. is not willing to risk a broader war with Russia by sending troops to fight alongside Ukrainian soldiers. So, military options should look to asymmetric responses that keep us from potentially escalating to a nuclear conflict. One such option is to threaten Russia’s earlier attempts to establish buffer zones through so-called “frozen conflicts.”  

In Georgia, Russia has created two autonomous zones through frozen conflicts — Abkhazia in the Black Sea region and Ossetia in the north. In Moldova, a small Russian force remains inside the breakaway Republic of Transnistria, which borders Ukraine. These outposts of Russian expansion are exposed and vulnerable to military action by Georgia and Moldova, if supported by the West. Most importantly, threatening these outposts does not threaten Russia proper, because unlike Crimea, Russia does not declare them as Russian territory. Reinforcing Moldovan and Georgian forces to create a credible threat to retake these breakaway regions would require Russia to divert military forces from any plan against Ukraine — perhaps enough to throw the plan in doubt.  

The U.S. and its Western supporters also could threaten to conduct a blockade or quarantine of the Russian exclave Kaliningrad, surrounded by Poland and the Baltic Sea. Such a step would stress Russian military resources, especially when coupled with build-ups around the Russian outposts in Moldova and Georgia.   

Finally, Turkey could play an unexpected role if the U.S. and West can convince it that Turkey’s security is also threatened by an expansionist Russia. Under the Montreux Convention, a treaty that regulates the passage of ships between the Black Sea and the Mediterranean Sea, Turkey has control over the strait connecting the two bodies of water. In accordance with Articles 20 and 21 of the convention, if Turkey feels it is in “imminent danger of war,” it has the right to permit or restrict the passage of any ships it chooses. Turkey could declare that a war in Ukraine would present a danger to Turkey, allowing it to grant passage to an unlimited number of Western war ships while restricting Russian passage. Such a step would quickly tilt the balance of power against Russia in the Black Sea region — something Turkey might find beneficial to its own long-term security interests.   

We cannot know what choices President Putin will make with regard to Ukraine, but he has assembled the resources to give him several credible military options. If we want to prevent such a choice, it would be prudent that the U.S. and the West do the same. That means not just “saying” we would take steps, but moving the troops and equipment so that we “can” take steps if we choose. This is the kind of messaging that Russian leaders understand.  

Retired Brig. Gen. Kevin Ryan is a senior fellow at Harvard Kennedy School’s Belfer Center. He served as U.S. Defense Attaché to Moscow and director of Army Strategy, Plans and Policy (G35) at the Pentagon.