IIRC, the first triumvirate originally intended for Pompey to be the one to invade Parthia, but he was too in love with his wife to leave her, and so Crassus went instead.
What if Pompey had invaded Parthia, as planned?
In 75 BCE, Pompey faced off against Quintus Sertorius at the Battle of Sucro river. During the fighting, he was wounded in the thigh.
What if he had been killed instead of just injured?