A Heritage Foundation report has ranked the U.S. military as "weak" for the first time in the annual assessment's nine-year history. 

The conservative think tank's 2023 Index of U.S. Military Strength warned that the force is at a growing risk of "not being able to meet the demands of defending America's vital national interests."

"It is rated as weak relative to the force needed to defend national interests on a global stage against actual challenges in the world as it is rather than as we wish it were," the Heritage Foundation said.

It cited years of sustained use, underfunding, "poorly defined priorities," "wildly shifting security policies," "exceedingly poor discipline in program execution" and "a profound lack of seriousness across the national security establishment."

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The Heritage Foundation said the index assesses the ease of operating in key regions, regional political stability, the presence of U.S. military and the condition of key infrastructure.

The condition of the U.S. military's power is measured in terms of modernity, capacity for operations and readiness for missions.

Lloyd Austin

Secretary of Defense Lloyd Austin attends a press conference at Ramstein Air Base on Sept. 8, 2022, in Ramstein-Miesenbach, Germany. (Thomas Niedermueller/Getty Images)

Highlighting acts from Russia, China, North Korea and Iran – including Russia's invasion of Ukraine – the index noted that the U.S. must be able to defend its interests in more than one region at a time "no matter how much [it] desires that the world be a simpler, less threatening place."

The Heritage Foundation added that its report is based on the ability of the military to defeat two major competitors approximately simultaneously.

A 10th Mountain Division soldier fires his weapon during a training exercise in Arta, Djibouti, on Aug. 25, 2018.

A 10th Mountain Division soldier fires his weapon during a training exercise in Arta, Djibouti, on Aug. 25, 2018. (U.S. Air Force photo by Senior Airman Haley D. Phillips)

The think tank said it acknowledges that, without a dramatic change in circumstances, administrations will allocate funds to domestic programs.

Ultimately, an evaluation of each military branch found the Marine Corps was "strong" while the Air Force was "very weak."

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The Navy and Space Force were "weak," and the Army was ranked as "marginal."

The U.S. nuclear capability – which was treated as a separate entity – was found to be "strong" but trending toward "marginal" or "weak." 

The Heritage report concluded that the military is at risk of not being able to meet the demands of a single major regional conflict while also operating elsewhere, noting that modernization programs suffer and that there have been reductions in the size of military units.

President BIden

President Joe Biden speaks during a meeting at the White House on Sept. 26, 2022, in Washington. (Kevin Dietsch/Getty Images)

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The index said the Biden administration's proposed defense budget falls short of what is necessary.