The American people aren’t fully conscious of the strategic threats the nation faces today, especially from near-peer nuclear adversary nations such as China and Russia, the head of U.S. Strategic Command said Monday at the Pentagon.

The threat was apparent during the Cold War, but 70 years without a great power conflict has resulted in people taking strategic deterrence for granted. Adm. Charles A. Richard said it was not just some fate in history that America was never attacked with nuclear weapons.

“It was a lot of hard work by a lot of people to maintain systems ready to go, so we could deter that from happening,” he told reporters. “We don’t even think about that anymore.”

Based in Omaha, Nebraska, U.S. Strategic Command is responsible for the nation’s arsenal of strategic nuclear weapons. Adm. Richard said he couldn’t comment on reports of a new “secret weapon” in Bob Woodward’s upcoming book, titled “Rage,” about the Trump administration.

“I have not seen” the book, he said to a reporter’s question. “I’m not in a good position to help you address that question.”

China, the nation’s primary strategic threat, is expected to double its nuclear stockpile by the end of the decade. But merely measuring the stockpile is a “relatively crude” measure of China’s capabilities, Adm. Richard said.

China, in particular, is developing a stack of capabilities that in my mind is increasingly inconsistent with their stated ‘no first use’ policy,” he warned. “As a military commander, what I look at more is another nation’s capabilities and less about what their stated intentions are.”

What keeps him up at night, Adm. Richard said, is China’s ability to identify an objective and carry it out. He identified China’s coast guard as an example. It didn’t even exist until 2013 and now has 255 ships in its fleet.

“I think their strategic forces are next on their ‘to do’ list,” Adm. Richard said. “When China sets its mind to something, they’re very impressive in their ability to go accomplish something.”