I read that before the war Russians expected from Austria to remain neutral and friendly toward them as sort of thank you after they helped them to crush Hungarian revolution only few years previously in 1849.
So why did Austria only few years after Russians helped them to crush revolutions in their empire decided to act so aggressively toward Russia during war?
They mobilized more than 200 000 soldiers, kept that large army mobilized for almost 3 years (that being massive strain on empire finance), occupied Wallachia and put those soldiers in offensive posture on Russian border and forced Russia to keep a lot of their troops there instead fighting French/British on Crimea.
And than as final nail 1856 they threatened they gonna join war on Franco/British side if Russia doesn't surrender to Allies. Obviously after the war Russians were angry at what they perceived as great betrayal and that led to eventual rivalry over Balkans that was one of main factors of WW1 later.
And of course it let Austria vulnerable to later Prussian and French aggression and losing control of North Italy and leadership in Germany in 1859 and 1866.
So my question is why did Austrians done that, seems illogical to lose such a powerful ally who only helped them few years previously over Crimea, territory that Austrians didn't care anyway?
Source: reddit post