In this scene, early in the movie, Lawrence quotes Themistocles. "I cannot fiddle, but I can make a great state from a little city".
Background: Themistocles's leadership and tactics were the major driver in Athens' defeat of the ruling Persian empire. Without him, Athens probably would never have defeated them and become the leading power in their region of the Mediterranean.
Likewise, Lawrence's leadership and tactics were a major component in the Arab tribes' defeat of the Ottoman Empire and their independence.
What most don't realize is that Themistocles was later ostracized, driven from Athens, the city-state he helped to created. The same thing essentially happens to Lawrence, driven away from Arabia at the end of his story.