Complex sentence: After a five hour and twenty minute trial on September 15,1921, prosecuted by Yemelyan Yaroslavsky, Ungern was executed the same evening by a firing squad in Novonikolayevsk (now Novosibirsk, Russia).
Split into simpler sentences: After a five hour and twenty minute trial on September 15,1921, prosecuted by Yemelyan Yaroslavsky, Ungern was sentenced to death by firing squad. He was executed that evening by in Novonikolayevsk (now Novosibirsk, Russia).