Back in March, the Chinese government announced an 8.1 percent increase in its annual defense spending.

The increase brings China’s total reported defense budget to about $175 billion. But taken by itself, that number says little to nothing about the actual strength of the Chinese military.

Countries don’t go to war with budgets. They go to war with the forces those budgets support. The translation of money to manpower, ships, tanks, or aircraft can vary substantially from one country to the next.

Still, many critics often rely on gross spending comparisons as a rebuke of the U.S. military’s own $700 billion defense budget as excessive. That comparison is dangerous and misleading.

To begin with, no serious China analyst thinks the official Chinese defense budget accurately captures total Chinese defense spending. It almost certainly does not include, for example, Beijing’s substantial investments in space, and probably covers only a fraction of its cybersecurity spending.

“The 2018 Military Balance,” published by the International Institute for Strategic Studies in mid-February, estimated the Chinese defense budget for 2017 at roughly.

With that budget, the Chinese were able to support a highly modernized navy of 62 submarines and 83 major surface combatants—in addition to supporting the largest army in the world, and increasingly advanced air, space, and cyberwarfare capabilities.

The combined defense budgets of the United Kingdom, France, and Germany—the three highest-spending U.S. allies in NATO—total only $141 billion. These budgets support a combined naval fleet consisting of 26 submarines and 56 major surface combatants (of increasing age and declining readiness), and respectively smaller ground and air forces.

Clearly, too, there’s a difference in what money can buy from one country to the next.

However, there’s also a difference in how countries decide to invest. Defense strategies and investments should be determined based on a country’s strategy and interests, and the physical and political characteristics of the environment in which they expect to operate.

Just as these conditions vary, so will their defense budgets. For example, China and Russia focus their defense spending on requirements appropriate to their immediate geographic regions to support their geopolitical goals.

China has prioritized modernization of its naval forces and coastal defenses to secure its territorial claims in the South China Sea and to deny access to its competitors. These capabilities could put the U.S. at a disadvantage in a regional conflict with China in its home waters.

Russia, meanwhile, has invested heavily in ground combat vehicles and air defenses, and is concentrating forces in the Baltic region—potentially providing Russia with “local superiority” over NATO forces in the region.

The United States, by contrast, has global responsibilities, including supporting allies in both Europe and Asia. That means that the United States cannot focus its attention—or its forces—on a single region.

Thus, despite having a bigger budget and larger military, the superiority of U.S. combat power in a regional competition is by no means assured.

To ensure global stability, U.S. national security interests and the needs of its military—not misleading spending comparisons—must drive defense spending.