In recent years, the Russian government has capitalized on both melting sea ice and American inaction in the Arctic to dramatically expand its military footprint throughout the region. As Putin himself has put it, new shipping lanes opening in the Arctic may represent the future for the struggling Russian economy, but their presence in the region doesn’t only spell economic trouble for the United States, it also represents a threat to national security.

Now, American defense officials are beginning to sound off about the growing capability gap between the United States and Russia in the Arctic. Moreover, they’re also shining a light on how another global competitor—China—is poised to outmaneuver the United States in the frigid north.

“[China and Russia] both have…established a noticeably stronger foothold in the Arctic along the northern approaches to the United States and Canada,” Air Force Gen. Terrence O’Shaughnessy, commander of NORAD and America’s Northern Command (NORTHCOM) told the Senate Armed Services Committee on Tuesday. “As a result, the strategic value of the Arctic as our first line of defense has re-emerged and USNORTHCOM and NORAD are taking active measures to ensure our ability to detect, detract and defeat potential threats in this region.”

According to Maj. Gen. Laurie Hummel, who previously served as the adjutant general of the Alaska National Guard, Russia has built more than a dozen new airfields and 16 other military facilities throughout the Arctic in recent years. Those facilities include deep-water ports, dedicated training centers, and a number of paratrooper and electronic warfare units. These assets complement Russia’s fleet of more than 40 polar icebreakers, some of which are the only nuclear-powered icebreakers on the planet (at least for now).

The United States currently maintains only one troubled icebreaker capable of managing the heavy ice of the Arctic. There is an effort underway to build a single new icebreaker in the coming years, which will likely replace, rather than bolster, America’s icebreaker presence.

“They’re building 14 more, including nuclear-powered icebreakers, weaponized icebreakers,” said Senator Dan Sullivan, who has long championed the cause of Arctic defense from his vantage point in Alaska. “We’re finally getting our act together on that. Last year’s [National Defense Authorization Act] authorized six. But do we have the required capabilities to answer the Russian and, by the way, Chinese, challenge in the Arctic?”

American politics have placed a much larger emphasis on its southern border with Mexico. President Trump’s border security initiatives have met strong resistance from Democrats, who feel the construction of a barrier or wall is not the most effective means of border security. Some others that do support the idea of the wall have, however, taken issue with the president’s push to fund the wall immediately at the expense of other initiatives. As President Trump’s base squares off with his detractors regarding the southern threat, the Pentagon is keeping its eyes on the northern one represented by national militaries rather than illegal immigration.

“The Arctic is an area that we really need to focus on and really look at investing [in],” O’Shaughnessy said. “That is no longer a buffer zone. We need to be able to operate there, we need to be able to communicate there, we need to be able to have a presence there that we have not invested in, in the same way that our adversaries have.”

China, a nation with no formal rights to the Arctic, are actually positioning themselves to establish a presence in the region as well—a strong indicator of the strategic and economic importance of the region.

According to a European Parliamentary Research Service report released last May, “[China] sought—and in 2013 gained—observer status in the Arctic Council, to prepare the ground for a future expanded foothold in the region.” The revelation that China is currently building a nuclear-powered ice-breaker—making them only the second nation on the planet to possess one—would seem to support their conclusions.

As a result of Russia’s rapid expansion throughout the region and China’s concerted interest, O’Shaughnessy contends that the Arctic is now America’s front line of defense.

“Along with our partners and allies, we must adapt to the evolving strategic landscape and associated challenges to ensure we are ready to operate in and through the Arctic in all scenarios, across all domains, and against any adversary,” O’Shaughnessy wrote in an op-ed for DefenseNews. “Our homelands are not a sanctuary, and the Arctic is the front line in our defense.”