Q: What exactly are tanks?

Put simply, tanks are armoured combat vehicles. They have a large cannon mounted on a turret, heavy armour to protect against enemy attacks and tracks that wrap around the wheels so they can cross rough terrain.

Most tanks are operated by three to five people, including a driver, commander and gunner. 

Q: When were they invented?

Tanks were first used in warfare during World War One. The vehicles were made by the British Royal Navy together with French car manufacturers to attack enemy trenches. They were called tanks to trick the Germans into thinking they were water carriers. 

Tanks were also used frequently during World War Two. Today, all major armies have tanks. They have replaced cavalryThe cavalry are soldiers who fight on horseback. on the world's battlefields. 

Q: What do modern tanks look like?

The design of a tank is vitally important. Faults can be fatal - in the 1970s, Swiss engineers noticed that switching on the heating in their Panzer 68 tank could cause the main gun to fire. Military experts say the best tanks have a balance of three core elements known as the iron triangle: firepower, protection and mobility.

Today, updated forms of Soviet tanks are an integral part of Russia's military force. They have snorkels, explosive armour, thermal imaging, a laser range finder and anti-tank missiles. Meanwhile, since 1945, all British tanks have had the facilities to make tea onboard. 

Q: How many tanks are there in the world?

Experts suggest there are approximately 73,000 tanks in the world today. Of these, roughly 20,000 are in storage and 24,000 belong to potential enemies of the UK.

Russia has more tanks than any other country, with 13,300, followed by the US at 6,300 and China at 5,800. Ukraine has 2,100 tanks. But the numbers do not tell the whole story. Germany has less than 300 tanks, but its Leopard II model is one of the most advanced in the world. 

Q: What is the tank biathlon?

Since 2014, Russia's Ministry of Defence has organised the tank biathlon world championships. Teams from more than a dozen countries, including China, compete to overcome obstacles including slopes, mounds and explosives.

So far, Russia has won the competition every year. The US and the UK have never competed. 

Q: Will tanks still be important in another 100 years?

Some military experts believe the importance of tanks is waning. In the future, most fighting will involve newer weapons systems operated by commanders far from the frontline, such as drones, long-range missiles and robots. 

But many believe tanks will never disappear completely. Humans will still need to travel through war zones, and tanks can protect them. Future tanks are likely to be smaller, have armour made out of lighter nano-materialsNano-materials are materials made using particles that are only 100 millionth of a millimetre. Tanks could be made out of graphene in the future.  and may even run on hydrogenThe first element in the periodic table, and the most common element in the Universe. Stars are mostly made up of hydrogen. fuel cells. 

With more drones in the sky, traditional camouflage will be combined with technology to make the tanks invisible to infrared cameras. "You can certainly see an end to tanks probably in the future, but not yet," says one defence expert.