Mark Sedwill, the government's national security adviser, in May 2018 revealed that the Royal Navy likely wouldn't have enough ships to escort its two new aircraft carriers and would rely on allied navies to protect the carriers during wartime.

The Royal Navy plans briefly to double its number of warships in the Persian Gulf following an attempted attack by Iranian forces on a British oil tanker on July 20, 2019.

(This first appeared last month.)

But the temporary increase in British warships in the region, from one to two, underscores just how few ships the Royal Navy can deploy even in an emergency.

Iranian boats tried to “impede” the British oil tanker near the Strait of Hormuz, the BBC reported. HMS Montrose, a Type 23 frigate, “was forced to move between the three boats and the tanker,” according to the BBC.

The British government claimed the attacking boats belonged to the Iranian Revolutionary Guard Corps militia. The IRGC also allegedly was behind several recent bomb attacks targeting oil tankers in the Gulf and surrounding waters.

Tensions have escalated in the Middle East following U.S. president Donald Trump decision unilaterally to withdraw the United States from the 2015 deal limiting Iran’s nuclear program. After Trump restored economic sanctions, Tehran resumed stockpiling uranium.

The July 2019 tanker incident compelled the Royal Navy to accelerate by several weeks a planned deployment to the Gulf by the Type 45 destroyer HMS Duncan. Montrose and Duncan together will patrol the Persian Gulf before Montrose returns to U.K. waters for maintenance.

Duncan sailed south through the Bosphorus on July 13, 2019. The destroyer had been in the Black Sea region for NATO exercises.

The previous plan was for Montrose to depart the Gulf before Duncan arrived. The destroyer’s accelerated deployment “will allow a continuous naval presence to be sustained in the Strait of Hormuz,” a British defense ministry spokesman told Jane’s.

The Royal Navy likely cannot keep two major warships in the Persian Gulf for more than a few weeks. After decades of deepening defense cuts, the Royal Navy possesses just 19 destroyers and frigates. Only a few of them are deployable at any given time.

London's new defense strategy, released in December 2018, promised to maintain the fleet but not significantly expand it.

Periodic cuts since the fall of the Soviet Union in 1991 have shrunk the British military roughly by half. The most recent rounds of cuts starting in 2010 eliminated, among other forces, two aircraft carriers, two amphibious ships and four frigates, plus the Royal Air Force’s maritime patrol planes and carrier-compatible Harrier jump jets. Uniformed manpower dropped by 30,000.

As recently as late 2017, there were rumors that the United Kingdom might try to offset the cost of the country's exit from the European Union by further cutting the military. Amphibious ships appeared to be particularly vulnerable.

Fortunately for U.K. forces, funding stabilized at around $55 billion annually. In 2017 and 2018, the government allocated the armed forces an extra $2 billion, combined, above planned spending levels, enough to employ 196,000 active and reserve sailors, soldiers, airmen and civilian personnel.

The extra money in part came from a $13-billion reserve fund for four new Dreadnought-class ballistic-missile submarines that the Royal Navy is developing at a total cost of around $39 billion, which is nearly as much as the entire British military spends in a year.

Banking on the higher level of spending to continue, officials plan on building and maintaining a fleet including two Queen Elizabeth-class carriers, six Type 45 destroyers, eight Type 26 frigates, five low-cost Type 31 frigates, seven Astute-class attack submarine, 24 patrol vessels, 12 minehunters, five amphibious assault ships and nine logistics ships, together embarking six helicopter squadrons and 48 F-35 stealth fighters.

But that fleet still mostly exists on paper. 

Mark Sedwill, the government's national security adviser, in May 2018 revealed that the Royal Navy likely wouldn't have enough ships to escort its two new aircraft carriers and would rely on allied navies to protect the carriers during wartime.

That the Royal Navy struggles to maintain two warships in the Persian Gulf reveals just how overstretched the fleet is.

David Axe serves as Defense Editor of the National Interest. He is the author of the graphic novels  War Fix, War Is Boring and Machete Squad.