Defense Spending 101: Part 4: Sizing the Force To Meet the Threat

As I said in my first post in this series, the analysis that should be used is to determine our vital national interests, determine the capabilities of those that threaten those interests, and then determine the appropriate force structure necessary to defeat, if necessary, these potential enemies.  In the last two posts (this post and this post), I focused on the determination of our vital national interests and the assessment of the threat to those interests.  In this post, I will focus on the final step--sizing the force needed to combat the threat.

This is the step that requires the most military expertise.  In the Department of Defense, this is done by developing operational plans to prevail in various scenarios (such as defend South Korea against a North Korean attack), and then determining the force (people and weapons) needed to carry out this plan.  The Combatant Commands develop and update the operational plans, and various parts of the Pentagon do detailed, deep dive analysis to determine the force structure necessary to execute the operational plan.

This is not a mechanical exercise.  There is a great deal of judgment involved in doing this analysis, and there is quite often sharp disagreement among different parts of  the Pentagon about the assumptions used to determine the force.  To give, but one example, the operational plan will tell you how many fighter and bomber sorties there needs to be during each phase of the plan.  In order to determine how this translates into the number of fighters and bombers, other assumptions come into play: how many fighters and bombers will be disabled by the enemy?  How many sorties per week can each airplane do given the need for maintenance?  Will air refueling be required?  If so, how many fighters need to be devoted to protecting the refuelers.  AS you can imagine, different analysts can come up with wildly different numbers of aircraft needed for each operational plan.

There are two other important considerations that come into play here in creating the defense budget.  

First, in determining the force structure that we will pay for in the defense budget, how many operations do we assume we need to execute at the same time.  Armed conflict is rare enough--particularly the operations needed against a peer or near peer foe--that an argument could be made that we only need to assume one operation at a time.  For example, we only need a force large enough to fight North Korea OR Iran, and not both at the same time.  The problem with this approach is that our enemies have a say in the matter.  If we are engaged in a military operation against North Korea, and only have the forces sufficient to fight one war at a time, there is a danger that Iran or China will take this as an opportunity for aggressive action.  For this reason, until recently, our military strategy was built on the assumption that we could be fighting two wars at a time.  As you might imagine, this could be rather expensive. The chart above shows the large difference in force structure that results from different assumptions about how many wars we fight at once.   In the Obama Administration, this was revised to a strategy of being able to deter and hold off another potential enemy, and not a full fledged engagement.  The military "must be capable of deterring and defeating aggression ... in one region even when our forces are committed to a large-scale operation elsewhere," the strategy states. It will be interesting to see the construct developed by the Trump Administration.

Second, while operation plans are focused on the fight we must be prepared for today, the defense budget must also make investments for the weapon systems we need in the future.  For example,, while our current fleet of F-18, F-15 and F-16 fighter aircraft might be adequate in executing an operational plan today, they may be too vulnerable against a more technologically able Chinese military in the future.  Accordingly, there also needs to be an assessment of the enemy 20-30 years from now in order to make sure that we still have the weapons need to defeat the enemy.  Accordingly, the defense budget includes research and development and investment accounts in order to ensure that the U.S. military can meet the threats in the future.  For the Air Force, this means replacing our satellite assets with more cable and robust satellites, building next generation fighter craft such as the F-35, and building a new bomber capable of operating against Russian and Chinese air defense systems of the future.  When I was at the Air Force, much of our attention was devoted to this part of the budget--deciding how to time and allocate this investment budget. The chart above shows the projected change in fighter air craft from the old to the new, with a future F-X fighter in the distant horizon.

Once again, this part of the analysis requires judgment calls that can result in quite different defense budgets.  Do we return to the two-wars-at-a-time construct? Adopt another construct?  Do we really need to invest in the super-expensive F-35 or will an upgraded F-18 suffice for at least some engagements? These are not easy questions, and the answers can drive big changes in defense spending.

Other Posts in this Series:

Defense Spending 101, Part 1: Don't Get Distracted By the Wrong Numbers
Defense Spending 101, Part 2: Determining Our National Interests
Defense Spending 101, Part 3: Evaluating the Threat