Some differences between father and son had first appeared during the Franco-Prussian War, when Alexander II supported the cabinet of Berlin while the Tsesarevich made no effort to conceal his sympathies for the French. These sentiments would resurface during 1875–1879, when the Eastern Question excited Russian society. At first, the Tsesarevich was more Slavophile than the Russian government. However, his phlegmatic nature restrained him from many exaggerations, and any popular illusions he may have imbibed were dispelled by personal observation in Bulgaria where he commanded the left wing of the invading army. Never consulted on political questions, Alexander confined himself to military duties and fulfilled them in a conscientious and unobtrusive manner. After many mistakes and disappointments, the army reached Constantinople and the Treaty of San Stefano was signed, but much that had been obtained by that important document had to be sacrificed at the Congress of Berlin.