Mommsen's most famous work appeared as three volumes in 1854, 1855, and 1856; it expounded Roman history up to the end of the Roman republic and the rule of Julius Caesar. Since Mommsen admired Caesar, he felt unable to describe the death of his hero. He closely compared the political thought and terminology of the ancient Republic, especially during its last century, with the situation of his own time, e.g., the nation-state, democracy and incipent imperialism. It is one of the great classics of historical works. Mommsen never wrote a promised next volume to recount subsequent events during the imperial period, i.e., a volume 4, although demand was high for a continuation. Immediately very popular and acknowledged internationally by classical scholars, the work also quickly received criticism.