Complex sentence: The concept originated with British and French imperialists, who sought to link the railways they had built in southwest China, Indochina and Malaya, but international conflicts in the 20th century kept regional railways fragmented.
Split into simpler sentences: The concept originated with British and French imperialists, who sought to link the railways they had built in southwest China, Indochina and Malaya. International conflicts in the 20th century kept regional railways fragmented.