WASHINGTON (Reuters) - For decades, Western navies have built ever larger, more expensive warships. Those vessels now look increasingly vulnerable to thousands of small, fast Iranian attack boats that could dominate the Gulf in the event conflict there.
In response, the U.S. Navy has sent almost its entire fleet of small patrol boats and minesweepers to the region, hastily refitting some to dramatically increase their firepower
Concerns over the Gulf, a key oil conduit, play into a much wider debate about whether developed navies waste their money in pursuing a small number of sophisticated ships. Perhaps, some argue, they should follow the example of poorer states like Iran, who invest in large numbers of smaller ships rather than a handful of larger vessels that could be easily sunk.
In readiness for any potential war with the U.S. Navy and regional allies, Iran's navy and Revolutionary Guard have poured resources into small gunboats.
That, military officials and analysts say, would allow them to launch potentially devastating ""swarm" attacks.
Iran has said it would close off the Gulf if it were attacked by powers, including the United States and Israel, who accuse it of developing nuclear arms.
Western militaries say they are more than capable of meeting any threat and analysts believe that, given the sheer weight of U.S. military force in the region, Tehran would inevitably prove the ultimate loser in any conflict.
But privately, officers worry that their navies are relatively ill-equipped to manage an initial onslaught. Even the loss of a single large Western warship, with a crew of 700 and a cost of running to hundreds of millions of dollars, would be regarded as politically catastrophic.
"We are very concerned with the small boat threat out of Iran," said one Western naval officer with considerable experience in the region, speaking on condition of anonymity.
"They've got thousands of them that come from a bunch of locations, armed with everything from two crazy guys with a machine gun all the way up to antiship cruise missiles. Very dangerous for an unsuspecting target."
Certainly, the lessons of the only recent conflict to involve the kind of small boat attacks likely in the Gulf -- Sri Lanka's three decade civil war with Tamil Tiger rebels -- make alarming reading.
After losing several of its larger warships to small boat "Sea Tiger" attacks, particularly suicide strikes, the Sri Lankan Navy largely withdrew them from the conflict area to fight back with much smaller Israeli-built Dvora and locally manufactured fast attack craft that bristled with machine guns.
The U.S. Navy currently has five small Cyclone-class patrol craft based in Bahrain, with five more on the way, making almost all of its 13 such craft deployed in region, a source familiar with the matter said.
Until recently, these craft, with a crew of less than 30 but almost a dozen machine guns or cannon mounted on their decks, had been seen as something of an irrelevance. Several had been sold off to other navies or scrapped. But now, they are being refitted and having ever heavier weaponry added.
Washington has also deployed more than half its entire minesweeper force - 8 out of 14 vessels - to the Gulf, with four of the remainder based in Japan but ready to sail to the region.
"There's just never been a focus on small ships," says Nikolas Gvosdev, professor of national security studies at the U.S. Naval War College. "Navies, and perhaps particularly defense contractors and shipbuilders, just tend to like larger ships."
That, some naval experts say, ignores the fact that it has often been mass produced small ships that win wars.
With the size of frigates and destroyers in particular, the workhorses of modern navies, ballooning in the six decade since World War Two, even some political leaders have become exasperated.
"A Royal Navy locked into a cycle of ever smaller numbers of ever more expensive ships," British Prime Minister David Cameron complained in the House of Commons shortly after taking power in 2010. "We cannot go on like this."
Large warships still have a crucial role, naval experts say. The U.S. Navy's giant aircraft carriers, in particular, are seen as crucial to its ability to project force as a global superpower.
But for many current or predicted tasks, be it operating in an increasingly contested Arctic, tackling pirates in the Indian Ocean or operating in the Gulf or an increasingly restive Southeast Asia, the answer could be a much greater number of smaller multipurpose ships.
This month, Britain's Ministry of Defense Developments, Concepts and Doctrine Centre (DCDC) released their blueprint for a new class of ship they believe could become the mainstay of the fleet - the "Black Swan-class sloop".
The DCDC estimate the cost per vessel could be as low as some 65 million pounds, allowing several to be built for the cost of one large state-of-the-art destroyer. With a crew that could be as low as eight or as high as 60 when circumstances demanded, its flight deck could operate either a large troop-carrying Chinook helicopter or a menagerie of unmanned drones and weapons systems, although such extras would cost more.
Inspired by the fast sailing frigates of the Napoleonic Wars and the corvettes, destroyers and submarines hunters of the Second World War, the "Black Swan" project is controversial. It remains far from clear whether the concept will be adopted and taken further.
Most of Britain's admirals rose through the ranks as officers on large warships, insiders say, and remain hugely attached to expensive, world-class large warships.
"There is always a schism between the big ship and the little ship community," said one officer on condition of anonymity. "Pushing the "Black Swan" is almost certainly career death."
Certainly, for now, the Ministry of Defense seems lukewarm at best. A spokesman told Reuters that studies had shown frigate-sized warships or larger remained the best way for the Royal Navy to meet its requirements, which included "complex war fighting scenarios".
"This... was merely a think piece that speculated on the future shape of the maritime battlespace and made a number of assumptions on future technology, much of which is not yet sufficiently advanced to commit future equipment plans to," he said of the "Black Swan" concept document.
The experience of the U.S. Navy in their attempts to build a not dissimilar ship, the Littoral Surface Combatant, suggests keeping things simple could prove far from easy.
The eventual vessel - stealthy, fast and displacing close on 3,000 tons - is not only rather larger than some of the initial concepts plan, but also strikingly more expensive. Having initially embraced the concept of a small, light vessel, the Pentagon changed its mind mid-process and demanded more armor and safety features.
Critics say the assorted competing demands meant the project ultimately ran out of control, although the U.S. Navy says the ships will be a powerful new system in its inventory.
In April, pressure group the Project on Government Oversight (POGO) reported that the first ship of the $120 billion fleet, the USS Freedom, had been plagued by a total of 648 "chargeable" equipment failures since its delivery in September 2008. They included engine failures and at least 17 serious cracks in the four year old hull.
Even before they reach their planned deployment ports in Southeast Asia as part of the Pentagon's strategic "pivot" , they have also enraged China - a nation with a uniquely particular historic sensitivity to being surrounded by western gunboats. An editorial in the Communist Party mouthpiece "People's Daily" last month said their arrival would help "spread the smell of gunpowder" across the region.
China's navy itself has long been built around small craft, and most of its top admirals commanded fast attack boats in the early stages of their careers. But in the last decade, Beijing looks to have become increasingly drawn to following the Western model of ever larger ships.
While analysts say China has struggled with its first aircraft carrier, a former Soviet carrier initially imported ostensibly to be used as a casino, it is now believed to be building several of its own from scratch.
"It's interesting," says Gvosdev at the US Naval War College. "They seem to be coming down with the same syndrome."
Reporting By Peter Apps; editing by Ralph Boulton