Complex sentence: Chase began developing the company's repertoire of well-known full-length ballets, as well as original works, amidst financial issues, until in 1945 Oliver Smith joined Ballet Theatre and became co-director with Chase.
Split into simpler sentences: Chase began developing the company's repertoire of well-known full-length ballets, as well as original works, amidst financial issues. Iin 1945 Oliver Smith joined Ballet Theatre and became co-director with Chase.