By only looking at the context clues of <em>debacle</em>, we can infer that word has a negative connotation: something bad happened in Russia that made the officer of the Czar felt that he had not choice but to leave the nation. So, <em>success</em> and <em>celebration</em> are not suitable.
Now, if we look the word in the dictionary, we can find that <em>debacle</em> refers to an event or enterprise that fails, has a breakdown or that ends suddenly and disastrously, often with humiliating consequences. So, <em>debacle</em> can be replaced by <em>failure</em>.