While Heidi was making every possible preparation for the family's vacation to Saint Petersburg, which was where the Tsar's Winter Palace was, which was the primary residence of the House of Romanov. Bruno had found himself back at work, where he immediately requested time off to attend the ball which the Tsar was throwing for some ceremonial reason or another.
Because of this, Bruno's request first went to the Chief of Staff, who passed it off to the Kaiser. And the result was an invitation to the Kaiser's palace. Because of this, Bruno was escorted out of the headquarters belonging to the Central Division of the German Army's high command, and was brought to the Kaiser's palace, which he had visited on three prior occasions in his life.
Once as a teenager where he defended his fiancée's honor against a prince who dared to sully her name. And twice when coming back from war as a way to personally debrief the Kaiser on what he had been up to.