Due to its commitments elsewhere, none of America’s carrier groups are patrolling in the vast Pacific Ocean, and manpower shortages are confining ships to port. With Communist China’s naval power growing by the day, the danger it poses is approaching a highwater mark.

“We live,” President John Adams wrote his wife, Abigail, in 1774, “in an age of trial.” To achieve a favorable outcome for liberty, he led the First Continental Congress to outfit “armed vessels” to defend against “the enemies of the United Colonies.”

Adams called the Navy America’s “wooden walls.” But over the years, those walls have often been whittled down when pennies needed pinching. In 1888, the future president, Theodore Roosevelt, said that it was “a disgrace to us as a nation that we should have no warships worthy of the name.”

Roosevelt warned that America’s coastal cities would even lie “at the mercy of a tenth-rate country” like Chile. Later, as assistant secretary of the Navy, he increased readiness, leading to victory over Spain. As president, he sent the Great White Fleet to circumnavigate the globe, speaking softly and brandishing a big stick.

Today, that stick is shrinking. In April of last year, a former member of the Board of Directors of the United States Naval Institute, Steve Cohen, laid out the stakes in the Sun. He noted that this year’s budget called for “decommissioning 24 active warships … in order to use the savings to start building a mere nine new ships,” while Beijing launches dozens.

Mr. Cohen wrote that “both the Navy’s top officer and two successive civilian administrations have repeatedly said that the Navy must grow to 500 ships,” more than double its current size. “Otherwise, the Navy will simply not be equipped to do the jobs demanded of it … in the South China sea but along vital sea lanes and in hotspots around the globe.”

America’s situation is akin to that faced by the cash-strapped Royal Navy after World War II. But when Britannia could no longer afford to rule the waves, it handed the duty to a fellow democracy, America, not the expansionist communist power of the day in Moscow.

Already, the PLA Navy’s numbers are beyond those needed for a defensive wall of steel. “China,” the Center for Strategic and International Studies wrote in June, “now possesses the world’s largest maritime fighting force, operating 234 warships to the U.S. Navy’s 219.”

Beijing hopes that defeating Free China will break the island chain that stretches from Japan to the Philippines, and Indonesia, unleashing PLA Navy on blue water. The Center warned that if the expansion carried on “at the current pace … China will grow increasingly likely to emerge victorious from interstate war, especially a prolonged great power war.”

Were Beijing to attack an American ally today, none of America’s mightiest ships would be in the neighborhood to meet the challenge. “The deployment of the USS Abraham Lincoln,” U.S. Naval News reported last week, “has left the United States with no deployed carriers in the Pacific Ocean at a time when they are needed most.”

The “shortfall of deployed carriers,” the U.S. Naval News wrote, was the price of “the buildup in the Middle East.” The “critical gap” will last “for at least three weeks … in a region where standoffs and incidents are common,” such as the August 19 collision between Communist Chinese and Filipino coast guard vessels.

Elsewhere, “Military Sealift Command,” U.S. Naval Institute News reported last week, is removing “crews from 17 Navy support ships due to a lack of qualified mariners.” On Wednesday, the Navy Times reported that the service has missed its recruiting targets “for two years in a row,” leaving it “short about 22,000 sailors.”

The expansion of China’s navy is on a scale not seen since the Axis Powers of the 1930s, and this Great Red Fleet won’t be flying the flag of peace like Roosevelt’s. America and its allies are forewarned. Being forearmed, though, will require greater resolve and more spending to prevent a future where communism rules the waves and the seas bow to Beijing.