A term to describe the relationship between two countries at war?

I know it's an odd question, but I have an essay entitled basically "Russo-German rivalry during the 20th century was the major influencing factor in Germany's development." At the moment, I'm writing about WWI but I'm not sure of the best term to describe Russo-German relations, as I don't think it was rivalry - I see rivalry as more competition - so far I have 'hatred' but I'm still not entirely happy. Any ideas?