Readiness solves nuclear war, terror, and WMD prolif but ground forces are key.

For our first example, what might happen if the United States does not continue its missions to defeat ISIL, al Qaeda, the Taliban, and other violent extremist groups around the world? One potential regret is enduring terror movements that continue to destabilize vulnerable nations and whole regions; harm captured peoples; exploit captured territory to train terrorists, raise funds, and attract new recruits; and export violence to the United States and its allies and friends.

It remains unknown whether currently deployed forces are sufficient to achieve U.S. objectives. In fact, the United States has steadily increased troop deployments to Iraq and Syria and extended the mission in Afghanistan. However, this analysis assumes that U.S. ground forces will remain engaged at their current levels against extremist groups in order to continue to degrade them. Therefore, we assume here that these troops could not be pulled away for other operations without ending this mission. It is also possible that countering violent extremists will require more troops if the mission changes—for example, if additional ground troops are committed to combat operations, such as those in Syria and Iraq. Total troop requirements would remain those shown earlier as the worldwide commitments.

For our second example, how might Russia take the same course in the Baltics that it has taken in Ukraine? Russian “volunteers” could enter and destabilize Estonia and Latvia, or worse, conventional forces could launch a surprise invasion and present a fait accompli to NATO. We estimate that against currently stationed forces, the Russians could reach the Baltic capitals in 36–60 hours. That would leave the President with few and bad choices. The President could negotiate for the Russians to leave and risk the fracture of NATO if negotiations and sanctions drag on for months or years, or the President could choose to launch a counteroffensive to retake NATO territory—against a nuclear-armed Russia that has threatened first use of nuclear weapons to defend its territory from conventional attack and prevent its military from being destroyed. While the risk of war with Russia is small, and the risks of escalation to nuclear conflict are smaller still, neither risk is zero. Since the human and financial costs of both would be catastrophic, it is prudent to hedge against them.

Instead, NATO—and the United States—might place armored brigades in the Baltics. These armored brigades, along with other U.S. and NATO forces able to quickly deploy on warning, would be capable of denying Russia a quick victory. Such forces could be permanently stationed or rotationally deployed. These ground forces would be supported by air and sea power from the United States and its NATO allies. The European Reassurance Initiative and the four NATO battalion tactical groups deployed to Poland and the Baltics have made an important statement of alliance commitment and an initial “down payment” on the forces needed, but are not yet close to the amounts required to deny Russia a quick overrun of the Baltics.

If the Russians attacked under this scenario, the United States and NATO would send air, sea, and land reinforcements to deny a Russian victory. Additional U.S. and NATO forces would be needed to defeat Russian forces and reverse any Russian territorial gains.

We will now assess the numbers of ground forces needed for the missions described above. We will begin with continuing infrastructure tasks, including training new troops, supporting joint missions, and current overseas missions. Adding the forces supporting current missions, we have a demand for 434,000 soldiers to support infrastructure tasks and current missions. This includes the troops who are rotationally deployed; those forward-stationed in Europe, South Korea, and other places; and those supporting generating- and strategic-force operations (but who are not in the GRF or available for other missions). How large of an additional force would be required to deter and defeat aggression in the Baltics (shown here in orange)? For the deterrent force, we estimate that a total of three armored brigades would be needed on the ground in the Baltics on the day fighting started, along with the two U.S. brigades and supporting soldiers already in Europe, and two other U.S. Army and NATO rapid reaction brigades (the 82nd Airborne GRF and the NATO Very High Readiness Task Force) that can deploy to the Baltics on warning. In the future, our NATO allies should be able to provide one or more of the three armored brigades needed. However, in the near term, it is unlikely that any one of these nations would be able to sustain a deployed armored brigade. Therefore, we assume that the U.S. would need to deploy two more armored brigades and a fires brigade in addition to the forward stationed forces already in Europe and the armored and aviation brigades already deployed in a “heel to toe” fashion. In total, 36,000 additional soldiers would be needed over and above those already forward stationed or rotationally deployed to Europe. When deployed at a 1:2 rotation ratio, keeping 36,000 soldiers on the ground in the Baltics requires 108,000 soldiers to maintain a continuous presence. Including the 283,000 soldiers forward deployed in or rotating to Europe and other theaters, and the 151,000 soldiers engaged in infrastructure activities, a total of 542,000 soldiers would be required for these activities alone. This number exceeds the 476,000 soldiers now planned for the regular Army, forcing the DoD to reduce day-to-day operations, continuously deploy 66,000 National Guard or Army Reserve soldiers, grow the regular Army, or take some combination of these measures. Worse, this leaves no margin for higher demands if deterrence fails and war breaks out in Europe, Korea, or elsewhere in the world. In wartime, therefore, the DoD might be compelled to suspend troop rotations to maintain sufficient numbers of forces to meet contingency needs. From this point on in this testimony, we will discuss wartime demand, with troops deployed without rotation for the duration of a conflict. Such extended deployments for the duration of the conflict will impose extraordinary strain on troops and their families. (We should also note that some troop rotation will still be needed within theaters, so battle-worn units can pull back from the line for rest, refit, and replacement of casualties). If troop rotations to all theaters are suspended, including the deterrent force in the Baltics, troop demands will decline somewhat. The additional demand in the Baltics would decline to the 36,000 soldiers deployed at any one time; demand for the combination of other theaters would decline to 146,000, while the demand for infrastructure forces would remain steady at 151,000 soldiers. The total troops needed for these missions would decline to 334,000 soldiers when on a wartime footing. Additional troops would be needed if the Russians were not deterred and decided to invade. To expel the invading Russian forces, we estimate that an additional 85,000 U.S. troops, including six armored brigades and associated artillery, aviation, headquarters, and other supporting troops, would be needed to defeat a Russian invasion (shown in brown), along with eight brigades and a similar number of troops from our NATO allies. This raises the total U.S. troops needed to around 420,000 soldiers. This includes soldiers tasked to conduct infrastructure missions, continue current missions around the world, and deploy the U.S. contribution to the NATO deterrent and war-winning forces shown above. Once again, this assumes a wartime footing for all of these troops with no rotations of soldiers. We now turn to a third example—a war resulting from a provocation cycle that escalates to a North Korean attack on South Korea. Current DoD force planning seems to focus on an invasion threat to South Korea from North Korean forces, as depicted on the map. But the threat is changing. A provocation cycle could escalate out of control and lead to an artillery barrage of Seoul, involving some of the 10,000 artillery pieces and multiple rocket launchers, firing from hardened positions that the DoD believes to be in range of South Korea.10 Or North Korea might collapse as a result of war or economic failure, leaving up to 200 nuclear, chemical, and biological program sites unsecured (as represented by dots on the map above)..11 In either event, a significant burden would fall on U.S. forces. To counter North Korean artillery, U.S. ground forces would need to provide forces to evacuate U.S. noncombatants; engineering, logistics, and maneuver units to sustain South Korean and U.S. operations to clear artillery within range of Seoul; WMD-elimination task forces to secure chemical or nuclear munitions deployed with artillery units; and ground combat forces to protect each of these types of units. South Korean forces would also be stretched to gain control over North Korean military forces, exert political control over territory captured, and deal with a massive humanitarian catastrophe—all at a time when the South Korean Army is decreasing in size by one-third from its peak.

For these reasons, countering an artillery barrage or North Korean WMDs would require significant U.S. ground forces.