The US hospital ship Mercy gets resupplied at sea.

Quantity has a quality all its own. The Navy announced this afternoon that it has changed the arcane rules by which it counts ships, adding 10 coastal patrol craft, two hospital ships, and a high-speed transport to what it calls the “battle force.” The new rules would also keep 11 cruisers the Navy plans to not-quite-mothball on the rolls.

Those debatable additions drew an immediate denunciation from the chairman of the House seapower subcommittee, Rep. Randy Forbes. Forbes, like many Republicans, is ever watchful for what they think is administration gimmickry to hide the full impact of the budget cuts known as sequestration. Another Hill source told me the new system was just too confusing because some ships might drop in and out of the count from year to year, making congressional oversight even more difficult.

So revising these arcane metrics may become a political hot button. (In fact, that already happened just last year). They also shed light on how the Navy is reimagining itself for the post-Afghan War world — and they expose the service’s open secret: the “battle force” isn’t actually a force for battle.

What is a warship, anyway? Aircraft carriers clearly count, with their on-board squadrons of attack planes. So do missile-laden submarines and destroyers. Whether the Navy’s smaller and more fragile Littoral Combat Ship is a “real” warship has been hotly debated. Hospital ships? Coastal patrol boats that aren’t seagoing ships at all? As strategically important as they are — hospital ships for disaster relief, the patrol craft for guarding the Gulf against Iran — designating them as “battle force ships” does muddy the waters, at least metaphorically.

“With America’s national security budget under severe pressure,” Rep. Forbes said in a statement, “it is imperative that the Congress and the American people be able to visualize just how radically sequestration is impacting American naval strength.” (Note how, for Forbes, the ship count is part of a much larger political debate).

“I am disappointed to see the Navy is now counting ships like Patrol Craft and Hospital Ships in its battle force fleet that only a year ago it chose not to count,” Forbes said. “As well, I do not believe that a ship put in a reduced status should be counted” — that’s the 11 obsolescent but still functional cruisers Congress has forbidden the Navy to retire.

The Chief of Naval Operations, Adm. Jonathan Greenert, has already insisted that he’s not trying an end run around the retirement ban. The cruisers will be taken out of active service only until there’s money to modernize them and send them back to sea, he said. They’ll even be preserved and monitored more carefully than ships “laid up” in the past.

“We’ve done it before with battleships, [but] this is going to be more sophisticated,” Greenert told reporters Monday. “As a minimum you sort of shrink wrap them, put dehumidifiers on them. We will have people assigned to the ships to monitor [their condition]. When we put ships ‘in mothballs,’ [by contrast], they float out there and nobody has to look at them.”

Nevertheless, those 11 cruisers will take a long, long time to get ready for missions in an emergency, more so than even ships undergoing major maintenance.

Yet at the same time the Navy wants to keep the 11 “laid up” cruisers in the “battle force,” it is taking out three ships that actually could deploy, namely the Navy minesweepers used for mine warfare training in San Diego. Minesweepers in the Persian Gulf will count as part of the battle force; minesweepers at the stateside training base will not. Similarly, the 10 upgunned Cyclone­-class patrol craft deployed on a long-term basis to Bahrain will be counted; patrol craft in the US would not.

Even better, whether a ship gets counted will depend not only on where it is but when. If theater commanders regularly request a particular class of vessel that’s currently not in the battle force, the Navy now says it will add it, “on a case by case basis,” to quote a leaked letter from Navy Secretary Ray Mabus. The key criterion will be whether the ships are formally included in something called the Global Force Allocation Management Plan. “This will be a temporary authorization to include these ships in the ship count,” Mabus wrote, “until the ships are no longer requested in the GFMAP or are retired (whichever occurs first).”

Making the battle force more representative of what forward commanders actually do and do not use is a worthy goal. But counting the same ship at some times in its career and not at others “involves a great deal of confusion,” said a Congressional source. “That does make it harder to conduct oversight.”

There is a method behind the madness, however. Here’s the secret: Despite the term “battle force,” the Navy doesn’t measure itself primarily against the demands of future wars.

It’s day-to-day “presence” around the world that drives the size of the fleet: hunting Somali pirates; keeping an eye on the Iranian, the Chinese, and other bad actors; showing the US flag in foreign ports; conducting disaster relief and training exercises to built partnerships with potential allies. Compared to pure warfighting, these missions can make use of — indeed, require — a much wider range of vessels.

When Adm. Greenert outlined his top priorities for reporters Monday, “forward presence” was Nr. 2, second only to preserving the nation’s submarine-based nuclear deterrent. Readiness for today’s missions was Nr. 3; new tactics and technologies for future threats was Nr. 4.  “Do we have the capability and capacity to defeat an adversary in a major contingency?” Greenert said. “That was Nr. 5.”

Is that a shocking statement for the head of the Navy? Or is it perfectly sensible for a world that saw its last major naval battle in 1944, where pirates, typhoons,  and terrorists in speedboats come up as often as provocations by major navies like China’s? Or is it just a repeat of testimony the Joint Chiefs of Staff gave before the House Armed Services Committee? Perhaps the confusing part of how we count the “battle force” isn’t the counting part at all: It’s the word “battle.”