The chairman of the Joint Chiefs of Staff brought a dire warning to Capitol Hill on Monday.: “In just a few years, if we don’t change our trajectory, we will lose our qualitative and quantitative competitive advantage,” Gen. Joseph Dunford told the House Armed Services Committee. The military will need “sustained, sufficient and predictable funding” or lose “our ability to project power.” He further added that unless the Budget Control Act was repealed, within four years, the U.S. military would either be "much smaller" or "a hollow force."

In May, President Trump requested an overall defense budget of $639.1 billion for fiscal 2018, which is $52 billion more than permitted by the 2010 Budget Control Act. Uniformed and civilian defense leaders have decried the strictures of the BCA ever since it was ratified in a budget showdown.

What does projected power mean? It’s the ability to operate wherever the United States chooses to do so. Why is it at risk? Chinese and Russian efforts to develop and build long-range missiles, sensors to find and fix targets, a new generation of electronic signal jammers, and other technologies that can force U.S. forces to keep away from their targets — broadly referred to as anti-access, area-denial capabilities.

The concept is not new. Wallace “Chip” Gregson, then the assistant defense secretary for Asian and Pacific security affairs, first used the term A2/AD back in 2010. “These [weapons] are designed to deny access to the Western Pacific region or to deny the ability to operate within that vital area,” Gregson said. “A2/AD systems threaten our primary means of projecting power: our bases, our sea and air assets, and the networks that support them.”

Dunford was preceded on Capitol Hill by a rare evening appearance by Defense Secretary James Mattis. In his prepared remarks, Mattis said that the threat to U.S. dominance from A2/AD capabilities is growing. “For decades, the United States enjoyed uncontested or dominant superiority in every operating domain or realm. We could generally deploy our forces when we wanted, assemble them where we wanted, and operate how we wanted. Today, every operating domain is contested.”

His testimony, which the Pentagon sent out to journalists before Mattis’ appearance before the HASC, describes how advanced radars, anti-aircraft missiles, and 5th-generation stealth aircraft are challenging U.S. military dominance in the air; how longer-ranged anti-ship missiles are threatening U.S. command of the sea; and how the “introduction of long-range air-to-surface and surface-to-surface guided weapons, advanced armored vehicles and anti-tank weapons, and tactical electronic warfare systems” imperils U.S. dominance on land.

This is not a distant threat. China watchers are increasingly concerned about anti-ship ballistic missiles such as the DF-21. Earlier this month, the Pentagon’s annual report on Chinese military power suggested that China is deploying weapons to its man-made islands in the South China Sea. Russia, too, is building new A2/AD capabilities and putting them in more places — like its top-of-the line anti-aircraft radar, the S-300 and the S-400, to Syria.

Mattis’s testimony highlights “rapid technological change” in general as a challenge to U.S. military dominance. That includes “developments in advanced computing, big data analytics, artificial intelligence, autonomy, robotics, miniaturization, additive manufacturing, meta-materials, directed energy, and hypersonics – the very technologies that ensure we will be able to fight and win the wars of the future.…New commercial technologies will change society, and ultimately, they will change the character of war.”