Earlier Thursday, North Korea fired four missiles into the sea off its eastern coast. Nothing new there. North Korea loves firing missiles.

What's different about this action, however, is the missiles employed. This time it was anti-ship cruise missiles. And they apparently traveled 120 miles.

This is a clear threat to United States aircraft carriers operating in the western Pacific: "Don't think you're invincible," North Korea is saying.

It's a message the U.S. must not ignore. While inferior to those of China and Russia, the North Korean anti-ship missile force is increasingly credible. As the Romans learned at Cannae, the Zulus at Rorke's Drift, and the Persians at Gaugamela, a resourceful commander can overcome a far superior force.

That's not to say that North Korean commanders are resourceful, it's simply to say that we must assume they are. If we do not, we risk great loss of life.

But we should also retain perspective. The U.S. Navy's deployed combat forces are well-led and well-trained. Just think about the organizational effort involved in ensuring thousands of people are fed, cared for, and able to fight effectively thousands of miles from land. And at present, the U.S. has multiple fleets and around 20,000 sailors and Marines at sea in the Pacific.

The chart below shows its present force disposition.

Note that the 7th Fleet and Pacific areas of operation are effectively interchangeable. And while the Carl Vinson group is now heading home to San Diego, the Ronald Reagan and Nimitz groups are early in their seven-month deployments.

It's also worth noting the bottom of the chart — the USS America and USS Bonhomme Richard are also deployed in the Pacific. And those ships carry the 15th and 31st Marine Expeditionary Units. As I've explained, each MEU carries 2,100 Marines and an array of tanks, armored vehicles, strike helicopters and jets.

The standoff with North Korea is escalating, but each side has different rationales for accepting that escalation.

North Korea wants the U.S. to reduce its ballistic missile-related pressure. It hopes that by firing missiles, President Trump will decide the risks of a bloody war are too great, and that he'll offer concessionary carrots instead of military sticks. On the flip side, via the U.S. Navy, the Trump administration wants North Korea to understand it cannot out-escalate the U.S.

Yet this escalatory posturing isn't simply focused at Kim Jong Un. It's also intended to send a diplomatic message to Beijing. The U.S. knows that China is deeply uncomfortable with the presence of large U.S. fleets in its neighborhood. The fleets are a way of telling China that if it wants the U.S. Navy to go home, it must pressure Kim Jong-un.

Of course, this is a very high stakes game. As former intelligence officer John Schindler explains, it is exceptionally difficult to assess whether North Korean leaders are even rational. But as the escalatory curve advances, the risks of miscalculation grow.

Correspondingly, so to do the risks of war.