Forecasting the Demand for U.S. Ground Forces

A tool for comparing potential military outcomes over the next 20 years

RAND modeled thousands of scenarios exploring how the future demands for U.S. Army Forces could change depending on U.S. policy decisions and shifts in global order. In the tool below, you can explore these potential future scenarios by modifying baseline assumptions about U.S. policy and global order. You can then compare the results across military outcomes, such as the number of interstate wars, U.S. military interventions. and troops needed for military interventions. You can also compare the results across geographic regions.

This tool evaluates projected trends in demand for ground forces based on future U.S. policy, international conditions, and types of conflict and interventions

RAND research modeled hundreds of scenarios exploring how demands for U.S. ground forces could change in the future. Based on that modeling, this tool allows users to explore potential future scenarios by modifying assumptions about U.S. policy and key aspects of the international order. After defining a scenario, you can compare the results across different outcomes, such as the number of interstate wars, U.S. military interventions, and troops needed for military interventions. You can also compare the results across geographic regions.

This tool was completed in February 2019, followed by security review by the sponsor and the Office of the Chief of Public Affairs, with final sign-off in April 2022.

Select Military Outcome

Select Scenario Assumptions

Modify key U.S. policies and trends in the international order to see how they are projected to affect trends in conflict and U.S. military interventions. More about these assumptions

U.S. Policy Assumptions

International Order Assumptions

Worldwide

Interstate Wars

Interstate wars Worldwide
Intrastate conflicts Worldwide
Risk of major power war involving the United States
  • baseline
U.S. military interventions Worldwide
U.S. ground troops involved in military interventions Worldwide
Heavy U.S. ground troops involved in military interventions Worldwide
U.S. combat interventions Worldwide
U.S. ground troops involved in combat interventions Worldwide
Heavy U.S. ground troops involved in combat interventions Worldwide
U.S. deterrence interventions Worldwide
U.S. ground troops involved in deterrence interventions Worldwide
Heavy U.S. ground troops involved in deterrence interventions Worldwide
U.S. stability operation interventions Worldwide
U.S. ground troops involved in stability operation interventions Worldwide
Heavy U.S. ground troops involved in stability interventions Worldwide
Interstate wars Central America/Caribbean
Intrastate conflicts Central America/Caribbean
U.S. military interventions Central America/Caribbean
U.S. ground troops involved in military interventions Central America/Caribbean
Heavy U.S. ground troops involved in military interventions Central America/Caribbean
U.S. combat interventions Central America/Caribbean
U.S. ground troops involved in combat interventions Central America/Caribbean
Heavy U.S. ground troops involved in combat interventions Central America/Caribbean
U.S. deterrence interventions Central America/Caribbean
U.S. ground troops involved in deterrence interventions Central America/Caribbean
Heavy U.S. ground troops involved in deterrence interventions Central America/Caribbean
U.S. stability operation interventions Central America/Caribbean
U.S. ground troops involved in stability operation interventions Central America/Caribbean
Heavy U.S. ground troops involved in stability interventions Central America/Caribbean
Interstate wars South America
Intrastate conflicts South America
U.S. military interventions South America
U.S. ground troops involved in military interventions South America
Heavy U.S. ground troops involved in military interventions South America
U.S. combat interventions South America
U.S. ground troops involved in combat interventions South America
Heavy U.S. ground troops involved in combat interventions South America
U.S. deterrence interventions South America
U.S. ground troops involved in deterrence interventions South America
Heavy U.S. ground troops involved in deterrence interventions South America
U.S. stability operation interventions South America
U.S. ground troops involved in stability operation interventions South America
Heavy U.S. ground troops involved in stability interventions South America
Interstate wars Europe
Intrastate conflicts Europe
U.S. military interventions Europe
U.S. ground troops involved in military interventions Europe
Heavy U.S. ground troops involved in military interventions Europe
U.S. combat interventions Europe
U.S. ground troops involved in combat interventions Europe
Heavy U.S. ground troops involved in combat interventions Europe
U.S. deterrence interventions Europe
U.S. ground troops involved in deterrence interventions Europe
Heavy U.S. ground troops involved in deterrence interventions Europe
U.S. stability operation interventions Europe
U.S. ground troops involved in stability operation interventions Europe
Heavy U.S. ground troops involved in stability interventions Europe
Interstate wars Eurasia
Intrastate conflicts Eurasia
U.S. military interventions Eurasia
U.S. ground troops involved in military interventions Eurasia
Heavy U.S. ground troops involved in military interventions Eurasia
U.S. combat interventions Eurasia
U.S. ground troops involved in combat interventions Eurasia
Heavy U.S. ground troops involved in combat interventions Eurasia
U.S. deterrence interventions Eurasia
U.S. ground troops involved in deterrence interventions Eurasia
Heavy U.S. ground troops involved in deterrence interventions Eurasia
U.S. stability operation interventions Eurasia
U.S. ground troops involved in stability operation interventions Eurasia
Heavy U.S. ground troops involved in stability interventions Eurasia
Interstate wars West Africa
Intrastate conflicts West Africa
U.S. military interventions West Africa
U.S. ground troops involved in military interventions West Africa
Heavy U.S. ground troops involved in military interventions West Africa
U.S. combat interventions West Africa
U.S. ground troops involved in combat interventions West Africa
Heavy U.S. ground troops involved in combat interventions West Africa
U.S. deterrence interventions West Africa
U.S. ground troops involved in deterrence interventions West Africa
Heavy U.S. ground troops involved in deterrence interventions West Africa
U.S. stability operation interventions West Africa
U.S. ground troops involved in stability operation interventions West Africa
Heavy U.S. ground troops involved in stability interventions West Africa
Interstate wars East/Southern Africa
Intrastate conflicts East/Southern Africa
U.S. military interventions East/Southern Africa
U.S. ground troops involved in military interventions East/Southern Africa
Heavy U.S. ground troops involved in military interventions East/Southern Africa
U.S. combat interventions East/Southern Africa
U.S. ground troops involved in combat interventions East/Southern Africa
Heavy U.S. ground troops involved in combat interventions East/Southern Africa
U.S. deterrence interventions East/Southern Africa
U.S. ground troops involved in deterrence interventions East/Southern Africa
Heavy U.S. ground troops involved in deterrence interventions East/Southern Africa
U.S. stability operation interventions East/Southern Africa
U.S. ground troops involved in stability operation interventions East/Southern Africa
Heavy U.S. ground troops involved in stability interventions East/Southern Africa
Interstate wars Mideast/North Africa
Intrastate conflicts Mideast/North Africa
U.S. military interventions Mideast/North Africa
U.S. ground troops involved in military interventions Mideast/North Africa
Heavy U.S. ground troops involved in military interventions Mideast/North Africa
U.S. combat interventions Mideast/North Africa
U.S. ground troops involved in combat interventions Mideast/North Africa
Heavy U.S. ground troops involved in combat interventions Mideast/North Africa
U.S. deterrence interventions Mideast/North Africa
U.S. ground troops involved in deterrence interventions Mideast/North Africa
Heavy U.S. ground troops involved in deterrence interventions Mideast/North Africa
U.S. stability operation interventions Mideast/North Africa
U.S. ground troops involved in stability operation interventions Mideast/North Africa
Heavy U.S. ground troops involved in stability interventions Mideast/North Africa
Interstate wars South Asia
Intrastate conflicts South Asia
U.S. military interventions South Asia
U.S. ground troops involved in military interventions South Asia
Heavy U.S. ground troops involved in military interventions South Asia
U.S. combat interventions South Asia
U.S. ground troops involved in combat interventions South Asia
Heavy U.S. ground troops involved in combat interventions South Asia
U.S. deterrence interventions South Asia
U.S. ground troops involved in deterrence interventions South Asia
Heavy U.S. ground troops involved in deterrence interventions South Asia
U.S. stability operation interventions South Asia
U.S. ground troops involved in stability operation interventions South Asia
Heavy U.S. ground troops involved in stability interventions South Asia
Interstate wars East/Southeast Asia
Intrastate conflicts East/Southeast Asia
U.S. military interventions East/Southeast Asia
U.S. ground troops involved in military interventions East/Southeast Asia
Heavy U.S. ground troops involved in military interventions East/Southeast Asia
U.S. combat interventions East/Southeast Asia
U.S. ground troops involved in combat interventions East/Southeast Asia
Heavy U.S. ground troops involved in combat interventions East/Southeast Asia
U.S. deterrence interventions East/Southeast Asia
U.S. ground troops involved in deterrence interventions East/Southeast Asia
Heavy U.S. ground troops involved in deterrence interventions East/Southeast Asia
U.S. stability operation interventions East/Southeast Asia
U.S. ground troops involved in stability operation interventions East/Southeast Asia
Heavy U.S. ground troops involved in stability interventions East/Southeast Asia

Field Definitions

U.S. Policy Assumptions

Our baseline assumptions for U.S. policy through 2040 are that military size and spending will slightly decline, existing U.S. force posture with remain in place, and existing alliances will remain in place. We modeled a number of other policy decisions and their projected outcomes based on the following definitions:

Military size and spending

Baseline
Slight declines in personnel (1%) and spending (4%) by 2040
Increase to modernize
Substantial increases in personnel (14%) and spending (57%) by 2040
Reduce for restraint
Substantial decreases in personnel (25%) and spending (20%) by 2040

Military force posture

Baseline
Existing U.S. force posture remains in place
Prioritize defense of European NATO allies
11,000 additional troops in NATO Europe
Prioritize defense of U.S. Asian allies
23,000 additional troops in U.S. Asian allies
Combine prioritization of European and Asian allies
34,000 additional troops in NATO Europe, U.S. Asian allies
Prioritize forces available for Mideast contingencies
5,000 additional troops in Kuwait, UAE
Withdraw U.S. forces from overseas
Remove all major concentrations of troops from U.S. overseas locations

Extent of U.S. alliances

Baseline
Existing U.S. alliances remain in place
Continued expansion
U.S. concludes formal defensive alliances with Georgia, Sweden, Finland, and India
Sharp pullback
U.S. withdraws from NATO, cancels defense treaty with the Philippines

Modify these assumptions in the tool ⤴

International Order Assumptions

Our baseline assumptions for international order through 2040 are that there will be a modest increase in trade between states and a modest increase in democracies. We modeled a number of other options and their projected outcomes based on the following definitions:

Importance of International Trade

Baseline
Modest increases in trade between states of roughly 5%, with regional variations
U.S. joins TPP, TTIP
U.S. membership increases trade between U.S. and other member countries by 10 to 40%
Fracturing of global trading system
System dissolves into four competing regionally-based blocs, decreasing trade between most state by 10-20%

Prevalence of democracy

Baseline
Modest increase in number of democracies, with limited reversals
Democratic reversals
Several key countries revert to anocracy, including Brazil, Nigeria, and Poland
Expanded democratic growth
Increase in democratic regimes in sub-Saharan Africa, Southeast Asia. Limited democratic experiments in parts of Eurasia.

Modify these assumptions in the tool ⤴

Methodology

The RAND tool for forecasting the demand for U.S. ground forces allows the user to estimate U.S. military requirements under a variety of assumptions. The model underlying these forecasts has four central components.

First, the model predicts levels of intrastate armed conflict in the current year. We fit a statistical model (a logistic regression model), using data from historical cases of intrastate conflict, to establish the strength of the association between intrastate conflict onset and its key determinants, including demographic factors, political institutions, and previous experience with conflict. The model uses these historical patterns to calculate the predicted probability that each state will experience intrastate conflict in the current year based on its projected characteristics. Each state is assigned either a ‘1' or ‘0' for ‘conflict' or ‘no conflict, where the probability of drawing a ‘1' is set to the predicted probability determined by the model. Next, the process is repeated for interstate war: we fit a model based on historical data to specify the relationship between interstate war and its key predictors, such as relative power, territorial disputes, and dyadic democracy, and we predict a probability of war for each pair of states. The model assigns either war onset or peace based on these predicted probabilities. The model similarly determines the likelihood of termination for all armed conflicts, providing a dataset of all ongoing armed conflicts, by state, in each year.

These forecasted armed conflicts provide opportunities for U.S. Army interventions. We consider three types of interventions. All states in the system may host a deterrent intervention if the risk of conflict outbreak is sufficient. States engaged in a current intrastate conflict or interstate war may be subject to an armed conflict intervention, where the U.S. will remain committed until the conflict ends. All U.S. armed conflict interventions might then transition to a stabilization mission when the conflict ceases, and any state that has experienced the cessation of armed conflict within the past 5 years may likewise host a post-conflict stabilization mission. In a process that parallels the forecast of armed conflict, the model predicts which states will experience an intervention in a given year, given factors such as U.S. alliance commitments, the economic status and strategic resources of the partner, and the potential threat facing the state, as well as which interventions will persist and which will conclude. The final component of the forecasting model provides estimates of troop size and type. We leverage historic U.S. military interventions to provide a categorization of U.S. interventions and their "typical" sizes and force mixes. We place projected future interventions into these categories based on their type and factors such as the level of threat or adversary strength, the size of the country, and its political relationship with the United States.

We repeat this process to produce forecasts of armed conflict and interventions for each year from 2017 to 2040, where each yearly forecast incorporates the predictions from the prior year. Since the forecasts are developed using predicted probabilities, the model's predictions about the onset and cessation of armed conflicts and interventions are partly probabilistic. That is, while states having higher predicted probabilities are more likely to draw a ‘1' than states with a lower predicted probability, they are not guaranteed to. This means the results can change each time the model is run. Additionally, since the components of the forecasting model are interconnected — for example, the model will only forecast the start of an armed conflict intervention if it has previously forecast the start of an armed conflict and U.S. deterrent interventions influence the propensity of future interstate wars in a region — slight changes in the model's early projections can ultimately lead to significantly diverging forecasts between different runs of the model.

To ensure the robustness of our forecasts, we iterate the entire process 500 times, and base our forecasts on both the average predictions across those iterations and their distribution. A single iteration of our model therefore involves the full simulation of each component for each year from 2017 to 2040, and each subsequent iteration then re-simulates the entire 2017 to 2040 period. We present the mean predicted trends in armed conflicts and U.S. Army interventions across these 500 iterations to demonstrate the most likely single outcome, as well as the 10th and 90th percentile projections to show the range of plausible forecasts.