The Future of the Navy's Amphibious and Maritime Prepositioning Forces
November 2004
Section 6 of 6
CHAPTER 1. 4. Measures of Capability Under the Options
The different approaches to structuring the amphibious warfare and maritime prepositioning forces described in Chapter 3 would provide differing capabilities. To evaluate how those force structures would compare with each other and with the Navy's plan, the Congressional Budget Office used various measures of both peacetime and wartime capability:
- The total number of amphibious warfare and maritime prepositioning ships in the Navy;
- The amount of amphibious lift available on L-class amphibious warfare ships, measured in terms of five traditional components: the number of troops, landing craft, and helicopters that can be carried as well as the amount of space for vehicles and cargo;
- The total amount of lift (amphibious lift, sea-based lift, and sealift) provided by amphibious warfare and maritime prepositioning ships;
- The total number of Joint Strike Fighters carried by amphibious assault ships;
- The number of expeditionary strike groups deployed in forward areas; and
- The time needed to deploy Marine infantry battalions in a hostile environment.
The Navy's principal mission in peacetime is to maintain a combat-credible forward presence. Thus, the most important measure of how well the amphibious force performs during peacetime is arguably the capabilities it provides on-station in three overseas theaters of operations: Europe, the Indian Ocean, and East Asia. In wartime, a better measure is how much actual combat capability the force can bring to bear in a particular period. The measures that CBO chose capture aspects of both the peacetime and wartime missions.
The strength of those measures is that they provide a clear picture of the kinds of capabilities that each option sacrifices in order to save money. Relative to today's capabilities, every alternative examined in this study would reduce forward presence by ESGs and decrease the number of Marine battalion landing teams that could be deployed. Those changes would take place fairly gradually: for example, under all of the options, the first reduction in the number of ESGs would occur in 2012.
The measures of capability used in this analysis have limitations, however. Probably the most important shortcoming is that, if sea basing can be made to work, it will fundamentally alter the way the Navy and Marine Corps conduct military operations. Only the last measure--the speed with which Marine battalion landing teams can be put ashore--captures some of that effect. But none of the measures demonstrate the operational maneuverability that sea basing would provide to the amphibious forces that were equipped for it. The ability to move quickly and unpredictably is highly prized by today's Navy and Marine Corps leadership. Unfortunately, CBO could not find an effective way to quantify that ability.
Number of Amphibious Warfare and Maritime Prepositioning Ships
The total inventory of amphibious warfare and maritime prepositioning ships under the Navy's plan and the four alternatives that CBO examined measures the overall capacity of the force. (In no situation, however, would the entire force ever be available to deploy to a conflict, because at any one time some ships would be undergoing long-term maintenance and some units would be in training.)
As with all of the measures used here, the Navy's plan would provide the largest number of amphibious warfare and maritime prepositioning ships: 57 by 2035 (see Figure 4-1). The less expensive alternatives would provide substantially fewer ships. Of those alternatives, Option 3 would produce the largest force, with 45 ships, followed by Option 1B, with 39 ships, because they would not buy the more expensive sea-basing maritime prepositioning ships. Options 1A and 2, which would invest in sea-basing capabilities, would result in much smaller forces: 31 and 32 ships, respectively. However, those two options differ in the speed with which they would reduce the force. Option 1A draws down the force less quickly than Option 2 does, so it results in more ships between 2016 and 2034 (even though it ends up with fewer ships than Option 2 by the end of CBO's projection period).
Total Number of Amphibious and Maritime Prepositioning Ships Under Alternative Force Structures
Source: Congressional Budget Office based in part on data from the Navy.
Amount of Amphibious Lift on L-Class Ships
As noted in Chapter 1, for decades the traditional measure of capability for the amphibious force was its ability to carry Marine expeditionary brigades or some equivalent unit. Amphibious-lift capability is measured by five components: the amount of cargo space (called cargo cube) available; the number of troops that can be transported; the amount of space for vehicles such as tanks and trucks (referred to as vehicle square); the number of spots for carrying rotary-wing aircraft (expressed as CH-46 helicopter equivalents); and the number of spots for carrying air-cushion landing craft (or LCACs).
Since the early 1990s, the Marine Corps's official requirement for lift has been 3.0 Marine expeditionary brigades. The Navy has been unable to afford enough amphibious ships to provide that amount of lift, so it has adopted the "fiscally constrained" goal of 2.5 MEBs. However, actual amphibious-lift capacity is measured by the smallest component. Today, the amphibious force has enough vehicle square for only 1.9 MEBs (although it has excess capacity in the other components of amphibious lift), so that number is the current capability. It is set to rise to 2.1 MEBs by the end of 2005 with the arrival of the first LPD-17 class ship. Under the Navy's plan, amphibious-lift capability would grow to nearly 2.5 MEBs by 2025 and remain there through 2035 (see Figure 4-2).
Components of Amphibious Lift on L-Class Ships Under Alternative Force Structures
Source: Congressional Budget Office based in part on data from the Navy.
Note: The five components of amphibious lift are the number of troops a ship can carry; its vehicle storage area, measured in thousands of square feet (or vehicle square); its cargo storage area, measured in thousands of cubic feet (or cargo cube); the number of spots for parking vertical takeoff and landing aircraft (expressed as CH-46 helicopter equivalents); and the number of spots for air-cushion landing craft (known as LCACs).
All of the alternative approaches in this study would result in less amphibious lift than the Navy's plan would. Option 1A would produce the greatest decline because it would cut the number of L-class vessels the most. By 2035, it would provide only enough amphibious lift for 1.3 MEBs. By contrast, Option 3, which would sacrifice sea-basing capability to maintain a larger L-class force, would provide enough amphibious lift for 2.0 MEBs--only slightly more than the amount available today. Options 1B and 2 would provide lift for 1.8 and 1.7 MEBs, respectively.
As is the case today, vehicle square would be the limiting component of amphibious lift under all four of the options for most of the period covered by this analysis. Troop space would also be in relatively short supply by 2035. (Figure 4-3 provides more detail about how the Navy's plan and the alternatives in this study compare in terms of those two key components.)
Lift Capacity for Troops and Vehicles on L-Class Ships Under Alternative Force Structures
Source: Congressional Budget Office based in part on data from the Navy.
Note: Vehicle square is vehicle storage area measured in thousands of square feet.
Total Amount of Lift on Amphibious Warfare and Maritime Prepositioning Ships
Amphibious lift is only one aspect of transporting and sustaining Marine Corps units in naval expeditionary operations. A broader measure of capability is the total lift for troops and equipment provided by the amphibious warfare and maritime prepositioning forces. Currently, that total is 4.9 MEBs--1.9 on amphibious warfare ships and 3.0 on conventional maritime prepositioning ships--although the Navy's goal is a total lift capacity of 5.5 MEBs. By introducing sea basing, the Navy's plan would achieve that goal but would change its composition--to 2.5 MEBs of lift on L-class ships, 2.0 MEBs on new sea-basing maritime prepositioning ships, and 1.0 MEB on conventional cargo ships similar to the maritime prepositioning vessels in the fleet today.
Of the alternatives examined in this study, Option 3 would provide the largest amount of lift: 5.0 MEBs in 2035 (see Figure 4-4)--less than under the Navy's plan but more than exists now. That higher capacity results because Option 3 would retain the largest number of conventional maritime prepositioning ships and forgo the Navy's and Marine Corps's sea-basing initiative. At the other end of the scale, Option 2 would provide the least amount of total lift--2.7 MEBs by 2035--because the goal of procuring more-survivable sea-basing maritime prepositioning ships would come at the expense of a larger overall lift force. Options 1A and 1B would provide 3.3 MEBs and 4.4 MEBs, respectively, by 2035, while keeping the amount spent on procuring the new ships that provide that lift at the historical funding level.
Total Lift Provided by the Amphibious and Maritime Prepositioning Forces Under Alternative Force Structures
Source: Congressional Budget Office based in part on data from the Navy.
Note: Total lift comprises amphibious lift on L-class ships, sea-based lift on sea-basing-capable Maritime Prepositioning Force (Future) ships, and sealift on conventional maritime prepositioning ships.
Number of JSFs Carried on Large Amphibious Assault Ships
Comparing the number of Joint Strike Fighters that the Navy's amphibious assault ships can carry highlights the importance of that aircraft, in the eyes of many Marine Corps officials, for future amphibious operations. The JSF is designed to have the range and payload to provide close air support to distant Marine operations ashore. The more JSFs available on amphibious ships, the better able the force will be to perform the close-air-support mission.
The JSF's importance is also reflected in the Navy's decision to design the new LHA(R) amphibious assault ship to support more flight operations by such aircraft. The first LHA(R)--what is being called Flight 0--is being designed to carry 23 JSFs. The Navy hopes that future versions of the ship--Flight 1--will carry up to 30 of those fighters. (For the purposes of this analysis, however, CBO assumed that all subsequent LHA(R)s would carry the same number of JSFs as the first one.) In addition, the Navy expects existing LHA and LHD class amphibious assault ships to carry 20 JSFs when the ships are configured in a carrier role. As a result, the Navy's plan would produce an amphibious assault fleet capable of carrying a total of 264 JSFs by 2035.
Of the alternatives, Option 3 would come closest to the Navy's plan because it would retain the largest number of big amphibious assault ships. By 2035, that option would provide the capacity to carry 218 Joint Strike Fighters, followed by Option 1B with 195, Option 2 with 172, and Option 1A with 126 (see Figure 4-5).
Total Number of Joint Strike Fighters Carried by Amphibious Ships Under Alternative Force Structures
Source: Congressional Budget Office based in part on data from the Navy.
Number of Forward-Deployed Expeditionary Strike Groups
Although amphibious-lift capacity has long been the traditional measure of capability for the Navy's amphibious forces, the amount of forward presence provided by expeditionary strike groups has grown in importance. Amphibious ships are often called on to respond to small-scale crises around the globe. For example, they are the military's tool of choice for evacuating U.S. personnel from a country or providing humanitarian aid because the Marine Corps units on those ships have the skills and equipment to transport goods and people between ship and shore. In many cases, amphibious ships do not operate together when they are forward deployed. A group of three amphibious ships will often split up to cover two or three locations and thereby extend those ships' unique capabilities to a broader area.
Under current practices for crewing, maintenance, and training, an average of about 2.7 ESGs are forward deployed at any given time out of the 12 in the fleet. Recently, senior Navy leaders, including Chief of Naval Operations Vern Clark, have suggested that the Navy experiment with rotating crews and marines to forward-deployed amphibious ships (rather than having a ship and its crew and marines return home between deployments) in order to provide more presence with fewer ships. A similar policy, called Sea Swap, is being used on some types of surface combatants. The Navy has found that Sea Swap allows Arleigh Burke class destroyers to provide about 35 percent more presence than ships of the same class not using crew rotation. If the Navy achieved the same results with ESGs and maintained 12 such groups, it could keep an average of 3.6 ESGs forward deployed. (As a practical matter, however, Admiral Clark has indicated that he hopes the use of crew rotation will allow the Navy to reduce the size of the amphibious force and still maintain roughly the current level of overseas presence.)
With current operating practices, the Navy's plan would provide the highest level of forward presence by ESGs (see Figure 4-6). Because all four options would cut the number of ESGs, they would provide less overseas coverage. Option 3 would put an average of 2.4 ESGs on- station by 2035--slightly less than under the Navy's plan--and Option 1B would provide 2.2 ESGs. Option 2, which, with respect to L-class vessels, is consistent with proposals to reduce the amphibious force to eight expeditionary strike groups, would keep 2.1 ESGs forward deployed, on average. Option 1A would keep only 1.8 ESGs on-station because it would make the deepest cuts to the L-class force.
Average Number of Expeditionary Strike Groups Forward Deployed Under Alternative Force Structures
Source: Congressional Budget Office based in part on data from the Navy.
Note: Sea Swap is the Navy's plan to rotate crews every six months to forward-deployed ships in order to increase the amount of forward presence they provide.
If the Navy could successfully rotate crews to amphibious ships, along the lines of Sea Swap, that picture would be brighter. Three of the alternatives would provide more forward presence than today's larger amphibious force, which does not yet employ rotating crews. By 2035, Option 3 would keep an average of 3.2 ESGs forward deployed, followed by Option 1B with 3.0 ESGs and Option 2 (which maintains a total of eight strike groups) with 2.8 ESGs. Only Option 1A would provide less than the current level of forward presence, with an average of 2.4 ESGs forward deployed at any one time.
Time Needed to Deploy Marine Infantry Battalions to a Conflict
The Navy and Marine Corps use the speed with which Marine battalion landing teams can be put ashore in a hostile environment--more than any other measure--to demonstrate the potential effect of sea basing. Today, with a total force structure of 12 expeditionary strike groups and three maritime prepositioning squadrons, the Navy believes it could insert 15 Marine infantry battalions into a theater of operations within 10 weeks (see the top panel of Figure 4-7). That estimate assumes that no land base on friendly territory would be available in the theater; instead, the marines on L-class ships would have to seize a beachhead and secure it before the battalions supported by the maritime prepositioning squadrons could be assembled and begin operating. The first battalions to arrive would come from the two ESGs that would be forward deployed at any given time. Another four battalions would come from amphibious ships surged from bases in the United States and would start operating by the fifth week. The nine battalions supported by the maritime prepositioning squadrons could begin operating (a few battalions at a time) in weeks eight, nine, and 10.
Time Needed to Deploy Marine Infantry Battalions in a Hostile Environment Under the Navy's Plan
Source: Congressional Budget Office based on data from the Navy.
Notes: Under the current timeline, the amphibious assault would begin in week 5 or 6. Under sea basing, operations could begin as early as week 2. MPF(F) = Maritime Prepositioning Force (Future).
According to the Navy and Marine Corps, sea basing would accelerate that process by at least three weeks. With a force structure of 12 ESGs (including 36 amphibious ships), two squadrons of sea-basing-capable MPF(F)s, and one squadron of conventional maritime prepositioning ships, the time needed to get 12 battalions deployed would drop from nine weeks to six weeks under the Navy's plan (see the bottom panel of Figure 4-7).
Put another way, sea basing would allow twice as many Marine infantry battalions to be in place by week six (12 battalions instead of six) as would be the case today, the Navy and Marine Corps say. Four of those battalions would be deployed by the second week: one from the first forward-deployed ESG to arrive and three from the first MPF(F) squadron to arrive. By the fourth week, four more battalions would be deployed, one from a second forward-deployed ESG and three from the second MPF(F) squadron. As would be the case today, additional battalions arriving on amphibious ships from the United States would deploy by the fifth week. Finally, by week 10, the three battalions supported by the conventional maritime prepositioning squadron would deploy. Thus, the Navy and Marine Corps would have the same total number of battalions operating after 10 weeks as they would today, but the bulk of those units would enter the conflict more quickly.
All of the alternative force structures analyzed in this study, because they would be smaller and less capable than the Navy's planned force, would deploy fewer battalions, sometimes less quickly, in 2025 or 2035 (see Figure 4-8). CBO compared the results for both years because the alternatives vary in the pace at which they would reduce the number of amphibious ships over time. In 2025, Options 1B and 3 would deploy fewer Marine infantry battalions to a conflict through week seven than the other alternatives or the Navy's plan because they lack sea-basing-capable MPF(F) squadrons. After that, however, they would deploy more battalions than Options 1A and 2 because of their larger conventional maritime pre-positioning forces. (Option 1B diverges from Option 3 after week nine because it has one fewer Marine infantry battalion to deploy.)
Time Needed to Deploy Marine Infantry Battalions in a Hostile Environment Under Alternative Force Structures
Source: Congressional Budget Office based in part on data from the Navy.
The same general pattern would hold true in 2035. Options 1A and 2 would get four Marine infantry battalions into the conflict by the second week, compared with only one battalion under Options 1B and 3. By week 10, however, Option 3 would deploy more battalions than any other option--a total of 14, compared with 12 for Option 1B, nine for Option 1A, and only seven for Option 2. However, this measure does not capture the investment in survivability that Option 2 would explicitly make. Theoretically, its single MPF(F) squadron would be better able to sustain operations in the event that antiship threats had not been completely eliminated from the theater of operations.
Implications of the Analysis
The central conclusion of CBO's analysis is that with respect to amphibious warfare and maritime prepositioning forces, less money spent on the force structure will mean less overall capability than exists today.(1) CBO found no alternative that would allow the Navy and Marine Corps to have substantially more overall capability than the current fleet but at a price significantly below what the Navy plans to spend on its amphibious forces.
Some important questions for the Congress (which CBO did not attempt to answer) arise from this analysis. Are the strategic, operational, and tactical benefits of sea basing worth their monetary cost? And if procuring those benefits means reducing the number of L-class amphibious ships, are they worth the loss of other capabilities? For example, the Chief of Naval Operations has stated that he considers speed one of the most important--if not the most important--criterion for determining what capabilities the Navy should procure. If a given capability allows the Navy to bring force to bear in a conflict faster than it can today, he favors investing in it rather than in programs that do not further that aim. Is the ability to advance the timeline of Marine amphibious operations by several weeks worth the many billions of dollars that a sea-basing capability will require or worth a cut of one-third in the number of expeditionary strike groups--a trade-off that senior Navy leaders are explicitly considering? Are the freedom of action and operational flexibility that might be gained with sea basing worth those costs? (As stated at the beginning of this chapter, CBO's measures of capability cannot capture the value of independent action or operational flexibility.)
The four options described in this study represent ways to defer significant increases in spending on amphibious forces for the next 30 years. In the meantime, the Navy could use the money not devoted to amphibious or maritime prepositioning ships to pay for other transformational efforts, ship programs, or needs. However, deferring that spending would have significant consequences for the size and composition of amphibious forces. Whether the Navy should make that trade-off is a matter for defense officials and lawmakers to decide.
| 1. | By contrast, CBO's analysis of the surface combatant force found that several alternatives costing less than the Navy's plan would leave the force larger and more capable than the current fleet of surface combatants. See Congressional Budget Office, Transforming the Navy's Surface Combatant Force (March 2003). |
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