Why are American aircraft carriers so useful to policymakers?

Because a Carrier Strike Groups offers two opportunities: diplomatic messaging and military destruction.

In diplomatic terms, the arrival of a CSG offshore signals either commitment or threat.

Foreign governments recognize the high logistical, economic, and human costs of a CSG visit to their waters. Correspondingly, when a CSG turns up, an allied nation is able to see and feel that America values them. But a CSG also reminds allies that their relationship with America is valuable. After all, when an aircraft carrier arrives with its complement of cruisers, destroyers, and submarines, American power is hard to ignore.

The U.S. Navy recognizes and doubles down on this perception, throwing parties for local leaders while at port. The simple point is that the pure size and technical capability of American aircraft carriers speaks to power. If Hollywood sends the message that America is cool, CSGs send the message that America is better as a friend than as an enemy.

On that point, a CSG's threat messaging power is also obvious. For a start, the aircraft that make up each CSG's Carrier Air Wings (the aircraft squadrons on a carrier) are very potent. Embarked on each CSG are at least 40 F-18 E/F fighter-bombers, an electronic warfare squadron of EA-18 Growlers (F-18 variants tasked to disrupt enemy communications, tracking, and targeting), an AWACS radar squadron of 4 or 5 Hawkeyes, and passenger transport planes. Oh, and each CSG also has around 20 helicopters tasked with anti-submarine warfare, combat search and rescue, and logistics.

To be clear, those aircraft offer a power projection capability unmatched by any other Navy.

But that's just the start. Because the other ships in a CSG also have their own power. A CSG's destroyer squadron and guided missile cruisers can shoot down enemy missiles (including ballistic missiles) and jets, destroy enemy ships and hit targets on land. And lurking below the surface is at least one (normally two) attack submarines.

Collectively, these capabilities enable a CSG to operate in a simultaneous defensive and offensive posture.

Of course, the carriers are not omnipotent. Growing Chinese and Russian anti-ship missile and submarine capabilities are concerning. Further, as much a CSG affords policymakers with flexibility of options, it also poses political risk. An administration that sends a carrier into combat with an advanced nation risks losing more than 6,000 Americans.

Nevertheless, assuming that the need is significant enough, at this moment, President Trump has unusual flexibility with which to deploy a large number of CSGs. Thanks to the GoNavy website we can see exactly why.

At present, there are three CSGs currently deployed. Nimitz is in the Indian Ocean, Reagan is in the South Pacific, and Bush is in the Mediterranean. In addition, Eisenhower and Roosevelt appear to be the current emergency response CSGs. They offer a short-notice surge capability in the event of a crisis.

Next are the Lincoln and Vinson CSGs. While they appear to be available, both were recently deployed and may not have renewed their training qualifications. Similarly, the Truman and Stennis CSGs have either just completed or are about to complete a year-long maintenance program (what the Navy calls "planned incremental availability"), but probably haven't yet requalified. The Washington is the only one totally unavailable: it is about to begin a multi-year upgrade.

Nevertheless, if the Navy had to put to sea in force, the CSGs could requalify while on their way to a crisis. This means that Trump could probably have five carriers on station anywhere in the world within a month, and nine carriers within six weeks. Even without other U.S. Military assets, those air wings would offer considerable warfighting potential.

Trump should consider deploying these carriers and, when ready, the USS Gerald Ford (the first Ford-class carrier) which enters service on Saturday. As the Washington Examiner has explained, in order to resolve the North Korean crisis, China must know America isn't playing games.