The "war" isn't really between Ukraine and Russia. The so called "war" is mostly between West and East Ukrainians. But there are major conflicts between Russia and Ukraine too.
Almost all of West Ukrainians hate Russia and want to be with Europe. Many East Ukrainians prefer be with Russia. And whoever has a different opinion, hates another. If I still lived in Ukraine, I would prefer Russia, and another Ukrainian (online) called me a Russian payed spy and many names; *** ***** **** for that.
After the Vote of whether to join European Union or stay with Russia, the result was: Russia. That's when more the a million protestors came out in Kiev.
Ukraine went into a Revolution, and many of its army divisions were out of control as to which side to chose and more. Ukraine being without military, Putin saw that as an opportunity to "take" Ukraine into something like a new Soviet Union or new Russian Empire.
There are claims (remember: claims) that US was planning to do something in the Black Sea and Putin needed to strengthen it's military base in Crimea.
With Putin using Force on Ukraine, Ukraine feared/fears that Putin wants Whole Ukraine. Putin does seem to want at least 1/3 of it.
Which war are you talking about? Ukraine and Russia are not in war now
The war is between Kiev and eastern Ukraine. It began a year ago, and that is too much ground to cover in this question. Here are some websites that should help you to learn.
Ukraine was once part of the Soviet Union, and Russia wants it back.
Money. As usual, as everywhere.
