Militaries will always be reluctant to give up major prestigious pieces of equipment—even when they are no longer fit for purpose.

Navies were very reluctant to give up battleships, but they became too vulnerable to air attack and required large crews, so the loss of a vessel was a catastrophe, not only because of the loss of a major capability, but also because of the loss of life.

The most shocking loss for Australians was probably the sinking by Japanese aircraft of British battleships HMS Repulse and HMS Prince of Wales in the South China Sea off Malaya in 1941. They were the first capital ships actively defending themselves to be sunk solely by air power while steaming in the open sea.

The loss of the ships and 840 crew was a major blow to Allied morale and proved to be an ominous prequel to the loss of Singapore, where some 15,000 Australians were to become Japanese prisoners of war.

Vulnerability from the air now holds true for all major surface vessels because they have little protection against missile attacks, particularly against hypersonic missiles. Surface vessels are expensive and the systems that can sink them are relatively inexpensive.

Air forces will be reluctant to give up crewed combat aircraft, but their high cost is a concern even for the US Air Force. Its vision is to have a smaller number of highly capable crewed combat aircraft accompanied by combat drones that would have multiple capabilities and could be sacrificed to gain an operational advantage. Drones piloted from the ground are already used for intelligence, surveillance and reconnaissance missions, and can conduct ground strikes, electronic attack, suppression or destruction of enemy air defences, communications relay, and search operations.

Anti-aircraft systems used by ground forces such as the FIM-92 Stinger also make crewed low-level ground-attack aircraft vulnerable to being shot down. The Stinger launches an infrared homing surface-to-air missile with a range of 8,000 metres that can strike aircraft at an altitude of up to 3,500 metres. Stingers cost around $160,000 each. This compares to the cost of, for example, the F-35 Lightning II (which also has a ground attack role) at around $110 million each.

The war in Ukraine seems to have underlined that main battle tanks have passed their use-by date. Even during the war in Iraq, we found that an American Abrams tank could be disabled by explosively formed projectiles produced in Iran for less than $100. M1 Abrams tanks cost around $13.5 million each.

The Australian Army has 59 M1A1 Abrams that began entering service in 2007; under phase 2 of Land 907, the tank fleet will be upgraded to 75 M1A2 SEPv3 variants of the Abrams. The price tag will be around $3.5 billion.

Russian tanks tend to have thicker armour than Western tanks plus explosive armour to protect them against rocket-propelled grenades. In Ukraine, they are being destroyed at an alarming rate (for the Russians) by a variety of man-portable anti-tank missiles and, according to Ukraine, munitions launched from drones. Ukraine is also concentrating on destroying fuel tankers. Without fuel, gas-guzzling tanks go nowhere.

The main anti-tank systems being used against Russian tanks are the UK-supplied NLAWs (next-generation light anti-tank weapon), which have a maximum range of 1,000 metres and cost around $50,000 per unit, and the US- and NATO-supplied FGM-148 Javelin anti-tank missiles, which have infrared homing, a range of 2,500 metres, and a price tag of around $330,000 per unit.

Ukraine is also using the AT4 Swedish 84-millimetre unguided, man-portable recoilless anti-tank weapon at around $3,000 each with a range of about 500 metres.

The Ukrainian military has released imagery of drone-launched missiles destroying Russian tanks, but it’s not clear what they’re using, or whether it’s possibly part of an information warfare campaign.

The US is reportedly planning to provide Ukraine with up to 100 Switchblade 600 tank-killer drones. The Switchblade 600 weighs 23 kilograms, is man-portable and can be set up in 10 minutes. It’s designed to fly up to 40 kilometres in 20 minutes, then loiter for another 20 minutes, giving it a total range of 80 kilometres). It attacks tanks at 185 kilometres per hours, employing a Javelin anti-armour warhead. A touchscreen tablet can be used to manually or autonomously control the munition. A Switchblade 600 reportedly costs around $10,000.

All of this suggests that it’s probably time to move on from tanks. The war in Iraq showed just how easily modern tanks can be disabled by insurgents using cheap, unsophisticated weapons in a built-up area or where tank movement is restricted. Ukraine has underlined the even greater vulnerability of tanks to a range of cheap and effective anti-tank weapons in a modern conventional conflict.