Scenario Analysis on a Ukrainian Insurgency


Russia looks likely to invade Ukraine in the coming weeks, if not days. The number of forces Russia has massed on the Ukrainian border would allow for incursions along three fronts simultaneously—from Russia in the east, Belarus in the north, and Crimea in the south. Europe is threatening sanctions and promising disgrace for Moscow, but it may soon face the most difficult question of retaliation: whether to provide vital support for a Ukrainian insurgency.

External support is a decisive factor in the success of an insurgency. The direct support of neighboring state military forces contributed to successful insurgencies in Bosnia, Afghanistan in the 1980s, Tajikistan, Congo, and elsewhere, according to a RAND study from 2001. Support can take many forms; safe haven, financial support, materiel deliveries, intelligence support, and training can all keep an insurgency operating even when under tremendous pressure from an occupying power.

This commentary examines the challenges and benefits for the members of the North Atlantic Treaty Organization (NATO) of supporting an insurgency in Ukraine, depending on how much Ukrainian territory Russia takes. Specifically, how might support for an insurgency work if Russia takes the Donbas; eastern Ukraine up to the Dnieper, including Kyiv; or the entire country? Six scenarios emerge: in three, the West provides support to Ukrainians who fight on against a Russian occupying power; in three, it does not, either because it is too politically risky or there is little to no organized insurgent force to support.

  • The riskiest scenario for allied Western nations is one in which Russia takes all of Ukraine and NATO members provide materiel support to insurgents. That sets up a dynamic in which every insurgent attack on Russian forces is an irritant between Russia and the West, and Moscow has at its disposal several impactful tools for retaliation, including cyberattacks and economic leverage.

  • The riskiest scenario in the “no support” category is if Moscow stops at the Dnieper River, taking half of Ukraine, including Kyiv. This leaves a rump Western Ukraine, with limited economic resources and few defenses, largely dependent on neighbors to the west for economic support and assistance, and with a refugee population that is likely to be sizable. In this scenario, the West also has the least amount of influence over what happens inside Ukraine. Rather than Moscow fighting for control in Ukraine, it is free to turn its attention elsewhere.

  • Providing no support to an insurgency, no matter the territorial picture, also raises the medium-term risk of emboldening Moscow to continue its threats to Europe unabated.


This piece makes several assumptions to inform the scenarios:

  • Russia has completed its territory takeover, dismantled the Ukrainian army within that territory, and is in a hold phase, focusing on subjugating the restive population. If the Ukrainian army is still organized and fighting, the conflict has not yet moved into an insurgency phase.

  • U.S. and European allies are capable of delivering lethal force and clandestine communications capabilities into Ukraine at a robust enough level to matter. In any taking of territory by Russia, there will still be a certain porousness to Ukraine’s borders with Poland, Slovakia, Hungary, Romania, and Moldova, in particular the mountainous regions in the southwest. NATO forces’ involvement in Afghanistan, Syria, and Iraq has armed them with decades of practice in train-and-equip missions.

  • NATO members are the presumed actors. While an official NATO role in supporting a Ukrainian insurgency is highly unlikely, the nations most likely to be involved are those in NATO, and Moscow will interpret the activity as “NATO aggression.”

  • Finally, Moscow would attempt to squash an insurgency with the same vigor and ruthlessness that it displayed in Afghanistan, Chechnya, and Syria.

Uncertainty and Decision: Two Factors

This scenario analysis looks at three options for Russian seizure of Ukrainian territory and pairs those options with a yes or no question: Will NATO members support an insurgency in Ukraine? Six scenarios emerge, each with implications for U.S. and European policy:

Explanation of the Scenarios

Scenario 1: Near Status Quo

The most modest option for Moscow is to take the Donbas, where fighting has been ongoing since 2014. The Russian Duma on Tuesday voted to recognize the independence of Donetsk and Luhansk, paving the way for Russian forces to “assist” their new neighbors.

After Russia has established conventional forces in the region, a follow-on insurgency would look like a shift in the status quo. Ukrainian forces currently fighting pro-Russian separatists and their Russian backers would have large numbers of Russian regular troops as new targets. Cut off from the larger Ukrainian army, these forces would need additional support in the medium term from outside the region and would need to reorganize into a guerilla force, rather than formal military units. Combatants would need a safe haven in the rest of Ukraine, along with supply routes for weaponry and other needed materials, because Russia could saturate the territory with regular and irregular forces.

This scenario probably contains the most limited implications for NATO and the West, likely resembling the annexation of Crimea in 2014.

Scenario 2: West Ukraine versus East Ukraine

As laid out in a recent piece by Seth Jones and Phil Wasielewski, Moscow may decide to move forces from the east and the north and take all the territory east of the Dnieper, including Kyiv. This divide echoes Berlin during the Cold War, with defectors attempting to move from east to west, and spies moving both directions.

Support for an insurgency would require routes for crossing the Dnieper with equipment and people. It would also require West Ukraine to have a functioning military and counterintelligence service, both necessary to support an insurgency on the other side of the border. The West Ukrainian government would need support from Europe—above and beyond the support provided to the insurgents in the east—to bolster its stability in the aftermath of a violent conflict and in the face of a committed Russian adversary. The insurgency would divide Russia’s attention, forcing it to prioritize disruption rather than additional annexation of territory.

The main implication of this combination is a West Ukraine under constant attack, but from a distracted Moscow. Moscow would seek to undermine the rump government of such a state with every tool in their tool kit, from cyberattacks to disinformation and propaganda directed at West Ukrainians. The Russian Main Intelligence Directorate (GRU), Federal Security Service (FSB), and Foreign Intelligence Service (SVR) would throw tremendous resources at penetrating the security services of a West Ukrainian government in order to disrupt support to insurgent forces in the east.

Scenario 3: Cross-Border Operations

While a total Russian takeover of Ukraine would take considerable time and maneuver, it is not impossible. In this scenario, Putin decides that all of Ukraine must come under Russia’s thumb, with no territory left as a threatening pro-Western presence. He would have total control over all the existing state instruments of power and President Volodymyr Zelensky and the Ukrainian government would be in exile, perhaps even assassinated in the fighting.

NATO assistance would be a critical lifeline to an insurgency in this scenario. Insurgencies are more likely to succeed if they have a safe haven—with no Ukraine left, there would be no internal respite for the fighters. NATO would also need to manage cross-border smuggling of materiel, with Russian troops in control of border crossings.

This scenario poses the highest immediate risk for the West. Every weapons shipment or attack will raise tensions with Russia. Moscow is likely to retaliate by manipulating energy and other exports and striking in the cyber domain, harassing NATO countries just as they feel harassed in Ukraine.

Scenarios without an Insurgency

Russia has a reputation for ruthless prosecution of military objectives. In Afghanistan in the 1980s, in Chechnya in the 1990s and early 2000s, and in Syria since 2015, Russia has spared little concern for civilian casualties or aimed for limited war. Under Russian control, there may not be a viable insurgency to support. Alternatively, NATO members may decide it is politically infeasible to support a Ukrainian insurgency. The following scenarios examine the same territorial ambitions but assume there is no viable insurgency.

Scenario 4: Crimea in the Donbas

If Russia limits its territorial gains to Donetsk and Luhansk and NATO decides it is too risky or infeasible to support an insurgency, the Donbas probably quickly begins to look like Crimea. Any resistance is likely to subside quickly due to a lack of resources and Russian tactics.

This scenario is likely if Western nations negotiate a deal with Putin or if Western pressure convinces Moscow that any transgression past the Donbas will result in broader conflict. In the medium to long term, Russia’s incremental creep toward renewed empire will continue, as Putin continues to press forward.

Scenario 5: Threatened West Ukraine

In a scenario where Russia takes the east of the country, Ukraine divides into a Russian puppet state in the east and a pro-European rump state in the west. Russia would seek to lock down the border between the two along the Dnieper.

A rump state in the west would need to establish a new capital, a functioning set of state institutions, and a viable economy, without the natural resources of the east. It would also face an influx of refugees from the east who seek to escape Russian rule. West Ukraine would turn to Europe for aid.

Whether that aid would be forthcoming is an open question. Europe did not step up to assist effectively with the Syrian refugee crisis, with many nations instead choosing to lock down borders. Afghan refugee flows may also increase in the coming months as winter drags on with little to no functioning government in Kabul, compounding the refugee arrivals in Europe.

The weaker West Ukraine seems, and the more secure Putin feels in East Ukraine, the more he may be tempted to take the rest of the country by force.

Scenario 6: Putin’s Big Win

Russia has amassed enough military forces along Ukraine’s border to take all Ukrainian territory and quash any attempted insurgency. NATO’s likely reaction to this development would be alarm and an attempt to bolster its periphery. Poland, Slovakia, Hungary, and Romania would seek reassurances of NATO support—perhaps fellow NATO member permanent troop presence—as would the Baltic countries.

Putin would be self-congratulatory, to be sure, for bringing Ukraine back to Russia’s orbit, and likely emboldened to pursue other objectives. This scenario is truly a big win for Putin and a black eye for Europe and the United States.


A divided Ukraine is marginally better than a total loss. The scenarios make clear that the loss of all Ukrainian territory to Putin is a threatening outcome for the West, whether or not an insurgency materializes. Should Putin’s advance divide Ukraine, assistance to West Ukraine will be essential. A weak West Ukraine, infiltrated by Russian intelligence agents, will see its attempts to assist an insurgency in the east gutted from within. West Ukraine in a totally defensive posture will be easy to drag into Moscow’s orbit.

There is risk on both sides. The scenarios highlight considerable risk in both supporting an insurgency and not. In any of the support scenarios, tensions between NATO countries and Russia rise. But failing to support a Ukrainian insurgency carries significant risks as well, not least of which would be opening the door to the next land grab by Moscow.

There are tangible and intangible benefits of support. Supporting an insurgency would distract Moscow from its continued efforts to undermine the West and send a clear signal that Western alliances will not crumble in the face of Moscow’s belligerence. Further, it would raise the domestic costs for Putin, as the Russian people link the loss of Russian soldiers to his adventurism. It would also demonstrate to those watching from the sidelines—such as Beijing, which will be drawing lessons for Taiwan—that changing borders by force will receive a rebuke.

Be prepared for the high human cost of an insurgency. The costs of an insurgency will be tremendous—NATO members are well aware of the bloody toll a conflict takes, after decades of involvement in Afghanistan and Iraq. The human suffering will be extended, as the median length of an insurgency is an estimated 10 years. Refugee flows will move into Europe over time; refugees will have less and less of their own resources to draw upon when they arrive as the war drags on. The geopolitical cost will also be high, as high-profile attacks on Russian troops in Ukraine become a constant source of irritation between Moscow and NATO members. The latter should expect retaliation in the cyber domain, perhaps against critical infrastructure, along with economic retaliation in key export areas for Moscow, such as aluminum and natural gas. Moscow has attempted to sanctions-proof its economy, including with over $631 billion in foreign reserves, giving it some staying power to withstand economic pain under all but the most dramatic sanctions and to exact some economic costs from its opponents. Russia provides an estimated 41 percent of the European Union’s natural gas imports and 27 percent of its crude oil imports; disruptions to Russian petroleum exports would also raise prices considerably.

Help the man in the arena. Despite the costs, NATO members should support any Ukrainian attempt to wrest control of the country back from Moscow’s grasp. The Ukrainian government and army have sent every signal that they intend to fight, and fight hard, to keep their country. Whether or not NATO supports this fight, Washington is likely to suffer a backlash, as Moscow will see the United States’ hand at play. In this case, it is better to enjoy the benefits of support if one must already suffer the backlash.

It is also likely that Moscow is underprepared to fight an insurgency. A December report by the Institute for the Study of War laid out what Moscow might need to quell insurgent fighting, given counterinsurgency doctrine on population ratios: “one counter-insurgent per 20 inhabitants . . . would suggest a counter-insurgency force requirement on the order of 325,000 personnel.” That estimate far outstrips the number of Russian troops amassed on the border, meaning Moscow would need to depend on local supporters.

To prepare support, NATO members should be caching materiel around Ukraine, establishing secure communications methods, and creating clandestine routes for moving people and equipment via land and air. Critical repair equipment, such as additive manufacturing machines, and document forging devices should also be in place as soon as possible. Some planning may already be underway—National Security Adviser Jake Sullivan told House members yesterday that “Secretary of Defense Lloyd Austin is looking to provide Ukrainians with military aid . . . to assist the resistance after a Russian invasion,” according to Politico

Prepare to be resilient. The Cybersecurity and Infrastructure Security Agency and other elements of the U.S. federal government have already issued warnings to alert businesses and government entities to the possibility of debilitating cyberattacks. The United States and European allies should immediately establish economic working groups tasked with creating contingency plans should Russia seek to exact economic costs for support. They should create a refugee working group as well. On the political front, shortly after an invasion begins, European nations should establish a negotiating team with a U.S. “observer.” That team should communicate to Moscow that it is prepared to talk to give Moscow an exit strategy to back out of Ukraine. Full U.S. participation can be a bargaining chip should Russia demonstrate it is willing to engage in withdrawal talks.

Putin holds it within his power to avert a great deal of suffering by standing down Russian forces. That could still happen if Putin claims “exercises” are over. Should he decide to invade, however, NATO members should stand in Russia’s way—and by the side of the Ukrainians.

Emily Harding is deputy director and a senior fellow with the International Security Program at the Center for Strategic and International Studies in Washington, D.C.

Commentary is produced by the Center for Strategic and International Studies (CSIS), a private, tax-exempt institution focusing on international public policy issues. Its research is nonpartisan and nonproprietary. CSIS does not take specific policy positions. Accordingly, all views, positions, and conclusions expressed in this publication should be understood to be solely those of the author(s). 

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Emily Harding
Director, Intelligence, National Security, and Technology Program and Deputy Director, International Security Program