A gloomy mood has descended over KyivThe capital of Ukraine.. Across the city, people are preparing emergency supplies. Just over 200 miles away, Russian troops are gathering on Ukraine's snowy eastern border. Many fear they are awaiting orders to invade. The people of UkraineA country in Eastern Europe. It was invaded by Russia in February 2022. are preparing for war. 

Today, senior US officials will meet with their European alliesAn ally is someone that aligns with and supports a cause with another individual or group of people. in Berlin. They fear that Russia could attack at "any point". 

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. is a military alliance - a group of countries that promise to defend one another if they are invaded. Russia has demanded that Ukraine never joins NATO. But the West has refused. 

Peace talks that took place last week were a failure. Now, 100,000 Russian soldiers are closing in on Ukraine and fears are growing. If war breaks out, it will be the first major conflictA state of disagreement when there is a difference of interests, values or goals. on European soil since the Balkan wars of the 1990s. 

Some Western officials believe Russia is looking for an excuse to invade Ukraine. They say Putin's motives are clear: last year he published an essay calling Russians and Ukrainians "one nation". 

Russia denies it is planning an invasion, but Putin has made it clear he will react if the West doesn't agree to his demands.

Since 2014, conflict in eastern Ukraine has killed 14,000 people and displaced 1.4 million more. A full-scale war could kill tens of thousands - and make millions more refugees. 

But there is still hope. Western leaders are still looking for a peaceful solution. And others think strict trading rules called sanctionsEconomic measures designed to punish a country, for instance by excluding it from trade. could stop Putin from invading by damaging the Russian economy. 

So far, the country has coped with Western sanctions, but more aggressive measures could be hugely damaging. In other words: war might be too costly for Russia. 

Plus, if large numbers of Russian troops are killed, Putin may lose his popular support at home. And war may bring NATO and Ukraine closer together rather than pushing them further apart.

Some think the costs of war could stop Putin. Others think he is determined to act. One thing is clear: war in Europe could have dire consequences not only for Ukrainians but for the entire continent - and even the world.

Yes: There is still hope. Peace talks and sanctions could persuade Putin that the risks of war are too great to continue. An invasion is not inevitable. 

No: Nothing will stop Putin from pursuing his goal of invading Ukraine. Last minute talks are doomed to fail. 

Or... No one can say for sure what Putin's intentions are. The build-up of troops may not be a warning about war. They might just be an attempt to bully Ukraine.