Simplify the following text for a Grade 8 native English-speaking person.
Original: By the war 's end , Austria-Hungary and the Russian Empire had collapsed and disintegrated ; Bessarabia , Bukovina and Transylvania proclaimed unions with the Kingdom of Romania in 1918 .
Simplified: By the time World War I was over , Austria-Hungary and the Russian Empire had fallen apart . This allowed Bessarabia , Bukovina and Transylvania to become part of the Kingdom of Romania again in 1918 .