Please answer a question about the following article about Roman Republic:

Clodius formed armed gangs that terrorised the city and eventually began to attack Pompey's followers, who in response funded counter-gangs formed by Titus Annius Milo. The political alliance of the triumvirate was crumbling. Domitius Ahenobarbus ran for the consulship in 55 BC promising to take Caesar's command from him. Eventually, the triumvirate was renewed at Lucca. Pompey and Crassus were promised the consulship in 55 BC, and Caesar's term as governor was extended for five years. Crassus led an ill-fated expedition with legions led by his son, Caesar's lieutenant, against the Kingdom of Parthia. This resulted in his defeat and death at the Battle of Carrhae. Finally, Pompey's wife, Julia, who was Caesar's daughter, died in childbirth. This event severed the last remaining bond between Pompey and Caesar.

Who was responsible for an expedition against the Parthian Kingdom?
Crassus