What are the motifs in When China Ruled the Seas: The Treasure Fleet of the Dragon Throne, 1405-1433 by Louise Levathes?

The spread of Chinese culture through sea domination is a recurring idea in the story. Zhu Di, third Emperor of the Ming Dynasty, was the ruler who ordered the building of China's first navy. The naval fleet, which was commonly referred to as the treasure fleet because it brought treasures home to China from other lands, consisted of literally thousands of cargo and warships during the peak of its dominance of the high seas.