Complex sentence: Russo-Perso War resulted with the invasion of present-day Azerbaijan territory by Russian Empire but after the collapse of the Russian Empire, Azerbaijan Democratic Republic established which was the first democratic and secular state in the whole Muslim world.
Split into simpler sentences: Russo-Perso War resulted with the invasion of present-day Azerbaijan territory by Russian Empire. After the collapse of the Russian Empire, Azerbaijan Democratic Republic established the first democratic and secular state in the whole Muslim world.