Why did Josiah strong write the predominance of the Anglo-Saxon race?

Josiah Strong wrote "The Predominance of the Anglo-Saxon Race" to promote the idea of Anglo-Saxon superiority and to advocate for the expansion of American influence, both domestically and abroad. He believed that the Anglo-Saxon race was destined to lead and civilize other cultures, reflecting a broader context of 19th-century Imperialism and racial theories. Strong's work aimed to justify American expansionism and the spread of what he viewed as superior cultural values.