Countries do not have friends. They have interests.
As you say, we have a common interest in this case...
...the last time we had a common interest we crushed The Axis.
“I cannot forecast to you the action of Russia. It is a riddle wrapped in a mystery inside an enigma; but perhaps there is a key. That key is Russian national interest. It cannot be in accordance with the interest of the safety of Russia that Germany should plant itself upon the shores of the Black Sea, or that it should overrun the Balkan States and subjugate the Slavonic peoples of south eastern Europe, That would be contrary to the historic life-interests of Russia.” - Winston Churchill (October 1, 1939)
Still a relevant statement today.