How to Use This Tool to Create a Custom Scenario for Defense Spending

This tutorial will walk you through how to use the various options in the Congressional Budget Office’s Interactive Force Structure Tool to create a scenario that matches the particular policy choices you want to explore.

For the purposes of the tutorial, we’ll use an illustrative scenario. The scenario is intended purely to show how the tool can be used. In other words, it isn’t some real policy proposal that we intend to evaluate seriously; it’s simply a learning exercise.

Step 1: Define Your Goals

The interactive tool can be used to explore simple “what if” changes (such as “what if we added an aircraft carrier?” or “what if we cut an armored brigade?”). In most cases, though, the tool will be more useful if you have a clear vision of what you're trying to learn about. That vision can take various forms. For example:

  • You may primarily be interested in the effects of adding to or cutting the Department of Defense's (DoD’s) budget, or
  • You may primarily have a vision of a particular type of force and be curious about how moving to that type of force would affect DoD's total costs, or
  • You may be interested in seeing what different types of forces DoD could sustain with a budget similar to its current one.

For the purposes of this tutorial, we're going to assume that we want to explore a large cut to DoD's overall budget—decreasing currently planned funding by about 10 percent. We don't want that cut to just reduce everything by 10 percent, though. We're going to focus the cuts mostly on reducing higher-end (and higher-cost) elements of the force, to see if we can maintain a robust force structure with less funding. In this sample scenario, we're trying to preserve lower-end and lower-cost elements of the force.

Step 2: Make Broad Adjustments—Using “Change the Overall Budget”

The first element of our sample scenario is to make a large cut, so we'll just enter the large cut first and then fine-tune it later. Open the interactive tool in your web browser and, on the Overall tab, find the header called Change the overall budget by. Here, we can adjust either DoD's projected annual budget 10 years from now (the end of the usual Congressional budgeting period) or DoD's total budget over 10 years. For this tutorial, let's accept the default setting and adjust the annual budget in the 10th year. We've decided that we want to see whether we can maintain a lower-cost, but still robust, force by shifting to a greater reliance on more basic forces. The total change in costs over the next decade isn't very relevant for that purpose.

We decided earlier that we want to reduce DoD's annual budget by about 10 percent. In the View Results table, we can see that DoD's planned force is projected to have an annual cost of about $889 billion 10 years from now. So we'll make sure to select “in the 10th year” for the type of change and then type in -89 (about 10 percent) for the size of the change.


As soon as we do that, several things in the tool change. You should now see, in the View Results table, that DoD's planned force has an annual cost of $888.8 billion in the 10th year, our custom force has an annual cost of $799.8 billion, and the difference is a reduction of $89 billion. The two results graphsTotal Costs and Number of Military Personnel—also now show cuts to each of the military departments: the Army, the Navy (which includes the Marine Corps), and the Air Force (which includes the Space Force).


To see how such a change might affect each of the military departments, you can go back up to where you clicked on the Overall tab and click on any of the departments. You'll notice that most of the sliders on the tabs for units in the military departments have been adjusted downward by about 10 percent. You can tell they've changed because the white circle (which represents the unit quantity or funding percentage in our custom force) has moved from the dark dot (which represents DoD's planned force). There are also negative numbers next to each slider, showing how much they've been reduced.


This is the interactive tool's default behavior when you change DoD's overall budget. The tool will try to spread the cut or addition in a proportional manner that preserves, as much as possible, the relative sizes of the different elements of the force. The tool can't always do that exactly. CBO included what it considers plausible limits on the minimum and maximum values allowed for each element of the force. For example, you can't increase the size of the B-52 force by 10 percent, because B-52s haven't been produced for decades, so it would be difficult to start building them again in the next decade.

For the purposes of this tutorial, we don't want to simply spread the total budget cut around in a proportional manner. So we'll fine-tune it a bit.

Step 3: Make Finer Adjustments—Using Sliders, Undo, and the Lock Buttons

For this scenario, we decided initially that we wanted to focus our cuts on higher-end units with higher costs. So let's go to the tabs for the different military departments and find units that look particularly pricey.

Selecting the Army tab, we can see different types of Army units. For each type, we can hover the cursor over the ? icon next to the unit’s name and see a quick description of that type of unit. We can also see the average annual cost and number of military personnel for that type of unit, including the unit’s share of support forces and administrative activities. (Those average annual costs and personnel numbers are based on DoD’s budget request for fiscal years 2024 to 2028. Fuller descriptions of the units and their costs can be found in The U.S. Military’s Force Structure: A Primer, 2021 Update, and a table with all of the units’ costs can be found under the Data and Supplemental Information header near the bottom of the tool.)

Looking at costs per unit, it's clear that Active-Component Armored Brigade Combat Teams (BCTs) are the most expensive type of unit in the Army ($3 billion apiece). The total budget cut that we entered in step 2 has automatically reduced the number of armored BCTs in the Army's active component from 11 to 10. We can reduce those units much more by clicking on the white circle in the middle of the slider and pulling it all the way to the left before releasing it. It now shows the number of armored BCTs reduced from 11 to 6—a larger cut.

We want to make sure that the change sticks and doesn't automatically get adjusted when we make other changes later. So we can click on the small lock icon next to the armored BCT slider. That will lock the slider at the value we selected.


Next, we can do the same thing on the Navy tab with that department's most expensive units, Carriers and Carrier Air Wings. Pulling those sliders all the way to the left will reduce the number of carriers to 7 and the number of carrier air wings to 5. We'll lock the sliders at those values as well.



Finally, we'll go to the Air Force tab and reduce the number of F-22 Fighter Aircraft Squadrons to 8 and B-2 Bomber Squadrons to 0. We'll lock in those values too.