Complex sentence: After World War I, there was strong interest in the major Norwegian cities of Bergen and Kristiania (which later changed its name to Oslo) in having larger orchestras, and in 1919 the orchestra in Bergen was reorganized to employed 40 professional full-time musicians.
Split into simpler sentences: After World War I, there was strong interest in the major Norwegian cities of Bergen and Kristiania (later Oslo) in having larger orchestras. In 1919, the orchestra in Bergen was reorganized to employed 40 professional full-time musicians.