The United Kingdom did more than any nation to pioneer armored warfare, and its Challenger 2 stands amongst the best tanks in the world. The sixty-two-ton tank established a reputation for exceptional toughness during combat in Iraq. But despite being a newer design than the Leopard or Abrams, the Challenger 2 has not been lavished with the extensive upgrades that its NATO peers have, and is generally perceived as having fallen behind.

In January 2017, the Ministry of Defense declared it had short-listed competing proposals from BAE Systems and German Rheinmetall for a modest Challenger 2 Life Extension Program (LEP) to improve the vehicle’s sensors and fire control computers. While the LEP is meant to increase the Challenger 2’s service life until 2035, neither proposal addresses the most glaring issues with the vehicle.

The Challenger 2 entered service only fifteen years after the Challenger 1 in 1983. At the time, it was the first British tank to benefit from state-of-the-art Chobham composite armor, which decisively restored the defensive primacy of modern tanks. However, the Challenger 1 still shared many systems with the preceding Chieftain tank, including a sluggish fire control system. The new tank performed poorly in exercises and suffered from extravagant teething issues. The Ministry of Defense was inspired to sign on to a more thoroughly modernized design in 1989.

Ironically, the Challenger 1 performed brilliantly under actual combat conditions in the Gulf War, destroying 200 to 300 Iraqi tanks without suffering any losses. The Challenger and Abrams were simply more than the Iraqis could handle. The Iraqi army was fielding older Soviet tanks that could not defeat such formidable armor—they might have had a fighting chance if they had improved ammunition. In return, the 120 millimeter guns on both vehicles could effortlessly pierce opposing armor. A Challenger 1 crew even achieved a record long-range shot during the conflict, destroying an Iraqi tank from 3.2 miles away.

But the Challenger replacement was already well underway. Despite its similar appearance, the Challenger 2 that entered service in 1998 had very few parts in common with its predecessor. It featured a longer barrel L30A1 cannon with a longer fifty-five-caliber barrel, and an upgraded composite package known as Dorchester armor, mixed with extra Explosive Reactive Armor (ERA) tiles. The latter type of armor involves metal plates sandwiched with explosives that explode outward against incoming projectiles, diminishing or deflecting the blast of shaped-charge warheads. In addition to the main gun, the crew of four can fire machineguns.

The Leopard 2, Abrams and Challenger are all considered to be broadly similar in capability, but the British design has some distinguishing quirks—notably, it was formerly considered the best armored of the three tanks, but also the slowest with a maximum speed of thirty-seven miles per hour. This latter trait is related to its underpowered 1,200 horsepower engine, compared to 1,500 horsepower powertrains on other top Western tanks.

The Challenger 2 is also noted for being one of the only modern tank design in its weight class to use a rifled gun. A rifled gun allows for greater accuracy, but the spinning motion it imparts leads to lower muzzle velocity, diminishing penetrating power for the kinetic armor-piercing sabot shells favored by most countries—which are quite stable anyway. But British tankers in the 1980s were more interested in their own unique form of ammunition, the High Explosive Squash-Head (HESH) which does not depend on kinetic energy for penetration, but still could benefit from the greater accuracy of a rifled barrel. HESH rounds employ a plastic explosive that generates a shock to the interior vehicle, causing metal to spall.

The Challenger 2 soldiered on in the U.S. invasion of Iraq in 2003, where it once again steamrolled opposing tanks around the city of Basra without suffering any losses to hostile fire. The British tank faced the greatest danger from roadside bombs and rocket-propelled grenades. One Challenger 2 was allegedly struck by seventy RPGs—and emerged with its crew unscratched. Another survived seventeen RPGs and a Milan missile, and despite the battle damage, was back in combat the next day.

The Challenger 2’s reputation for indomitability created somewhat unreasonable expectations. In 2007, it was revealed that a few years back an insurgent using an RPG-29—an especially powerful 105 millimeter warhead—had pierced through the belly armor of a Challenger 2 as it crested a dune. The belly armor is one of the weakest points on any tank. The penetrating warhead mauled the driver’s foot—though the vehicle remained in operational condition and was able to back away from the ambush. Another Challenger 2 was disabled in 2007 by an IED, but restored into operational condition. The only Challenger 2 to be totally destroyed was hit by another Challenger 2 tank by accident.

The Ministry of Defense was lambasted for having tanks that were not actually indestructible, and slightly more reasonably, that they had covered up the initial incident. Afterwards, the ERA armor on the lower front-hull was replaced with heavier Dorchester composite armor. Presently, the armor packages on the Challengers 2 breaks the scales at around seventy-five tons!

These were one of the few upgrades implemented on the Challenger 2, as the British military shrunk precipitously in the following years due to austerity measures. Meanwhile, Germany developed new models of the Leopard 2 tanks, and the U.S. Army has steadily phased in incremental upgrades to the Abram’s depleted uranium armor package and armor piercing ammunition. Thus, the Challenger 2 is now generally perceived to have fallen behind its NATO peers.

In 2017 the Ministry of Defense announced it would pay either Rheinmetall or BAE Systems 700 million pounds (roughly $900 million) to upgrade its Challenger 2s. The BAE proposal entails a new thermal and commander’s sights, as well as upgraded fire control systems. They would also install new computers that would improve on the 1990s-era displays and systems in the current model. The Rheinmetall proposals also offers a new electro-optical commander’s sight and sophisticated new sensors, including high-resolution cameras and a situational awareness system. The package would also include a Laser Warning System that would alert the crew if they were being painted by an enemy targeting laser, allowing them to back out of danger.

Combat experience has shown time and time again that the tank that detects, shoots at and hits the enemy first usually win. Sensors and fire control have traditionally been an area of strength for Western tanks compared to Soviet/Russian designs. However, neither upgrade addresses long-standing issues with the Challenger 2 or brings major new offensive or defensive technologies.

For example, one important new defensive technology which does not appear on offer is an Active Protection Systems (APS), which shoots down incoming missiles and rocket propelled grenades before they impact. These are precisely the kinds of weapons that most frequently threatened Challenger 2s in Iraq. APS systems have proven effective in combat on Israeli Merkava IV tanks, and are a major feature of Russia’s new T-14 tank and T-15 infantry fighting vehicle. To be fair, the occasions on which Challengers were struck by a dozen or more RPGs also provide a counterargument to the efficacy of APS systems, which might exhaust their countermeasures before the enemy runs out of antitank munitions.

Another issue is the Challenger’s quirky rifled gun and its ammunition. While HESH rounds have proven perfectly adequate for demolishing old Soviet tanks, modern tank designs with composite armor are very efficient at nullifying most nonkinetic warheads. In fact, German smoothbore guns of comparable barrel length and caliber have outperformed the Challenger 2’s rifled weapon.

Given that the HESH is less well-suited against newer tanks and the rifled gun barrel is incompatible with advanced 120 millimeter sabot rounds and air-bursting antipersonnel shells, replacing the L30 gun makes plenty of sense—and in fact, was repeatedly mooted by the Ministry of Defense in 2001 and 2008. However, the funding to implement that upgrade never became available, and the current proposals do not appear to contemplate a gun swap.

Finally there is the matter of the Challenger 2’s 1,200 horsepower engine which, despite its good reliability, struggles under the tank’s inflated weight. An upgrade to a 1,500 horsepower system would at least bring the Challenger 2 in line with other Western main battle tanks.

Of course, all of these upgrades would be expensive, and the United Kingdom faces difficult financial choices and competing needs—particularly with Brexit underway. In fact, perhaps the first important question concerns the role of the British army’s four remaining armored regiments, which are battalion-level formations. Sea and airpower, both of which are also poorly funded, might make greater sense as priority for an island nation. In what situations would the U.K.’s 227 tanks conceivably be relevant?

First of all, there could be peacekeeping missions such as those in Bosnia, or expeditionary forces deployed to conflicts like those in Iraq and Afghanistan. Though London is less eager to be involved in such conflicts in the post-Blair era, such operations remain a distinct possibility. While improving the Challenger 2’s protection against RPGs and IEDs would help for such missions—especially if they occur in an urban-environment—the current fleet would likely perform such missions adequately without major upgrades.