1. Why is Russia invading Ukraine? President Putin is worried that Ukraine will formally ally itself with Western countries that he considers enemies. In particular, he wants to stop it from joining NATOThe North Atlantic Treaty Organisation was founded in 1949 to unite Western democracies in Europe and North America against the perceived growing threat of the USSR. It now has 31 members.. For him, the best way to do this is to install a puppet government that follows his orders.

2. Why is it such big news? Because Ukraine is a neutral country that has done nothing to provoke Russia. An invasion like this has not been seen in Europe since World War Two and brings Russia into direct confrontation with the West for the first time since the end of the Cold WarA period of diplomatic conflict between blocs led by the USA and the USSR that lasted from 1947 until 1991, when the USSR collapsed.. With three million Ukrainians being advised to leave Russia, and others fleeing the territory Russia has invaded, it could also result in Europe's biggest refugee crisis since 1945.

3. Who is trying to stop Russia? NATO and the EU, as well as individual countries within them. All of them led by the US. France's President MacronEmmanuel Macron was elected as president of France in 2017 aged 39.  has tried to act as a peacemaker, so far unsuccessfully. Germany has imposed the strongest sanction: it has refused to approve the opening of the new Nord Stream 2A pipeline able to carry 55 billion cubic metres of gas per year from Russia to Germany under the Baltic Sea.  gas pipeline.

4. Can Ukraine's army stand up to Russia? Russia has the largest army in Europe. But Ukraine has the second-largest and has been well-armed by its Western allies. So far, Russian troops have been surprised by the strength of the defence from Ukrainians, so victory might not be as easy as Putin hopes.

5. Could sanctions work? They could seriously damage the Russian economy. But the effects would not be felt for some time, and Putin might feel that they were a price worth paying. Sanctions imposed when Russia invaded CrimeaA peninsula in southern Ukraine that was seized by Russian forces in 2014 and annexed to the larger country. did nothing to change his mind.

6. What is Putin's ultimate goal? Putin dreams of recreating a "Greater Russia" - making the country as large and powerful as it was in the 18th Century. This would involve bringing all the countries once part of the USSR back under Moscow's influence.

7. How important is gas and oil? Very. Russia is responsible for around 35% of Europe's supplies of both. If trading were disrupted, it would mean a massive fall in Russia's overseas earnings. But it would also mean a steep rise in energy prices, which could mean a loss of popularity for Western governments. 

8. Could it trigger other wars? Yes. If Russia can get away with invading another country in this way, it would set a dangerous precedent. The biggest worry is that China might follow its example and attack Taiwan.

9. Could our food supply be affected? Yes. Ukraine is the third-largest exporter of corn and the fourth-largest wheat exporter. If production is disrupted, prices could go up, leaving some countries facing shortages.

10. Could nuclear weapons be used? Possible but unlikely. Ukraine gave up its nuclear weapons in 1994 in return for a promise by Russia, the US and the UK that they would respect and protect its independence. Putin knows that using them could lead to a terrible escalation in the conflict, and is probably confident of winning without them.

Yes: For 75 years there has been an agreement among the world's most powerful nations, supported by international law, that invading a peaceful country is completely unacceptable. Putin has broken this.

No: Climate change, developments in AI and medical advances will all have bigger consequences. On a global scale, the invasion will be less disruptive than the Arab Spring or Covid-19.    

Or... It is impossible to say. The consequences of some events do not become clear until years later. Some people have lived with war all their lives and would not find this one remarkable.