Russian invasion begins: Why has Putin attacked Ukraine despite sanctions by world leaders? _Trailer

The news that Russia planned to invade Ukraine had occupied almost all the important pages of the media recently. The European Union, the United States, the UK, Australia, and Japan, and even the Canadian government, which just mobilized armed police to suppress peaceful demonstrators, have all said they intend to sanction Russia. So, why did Putin invade Ukraine in the face of united sanctions by Western governments?