Who was the leader of the Battle of Al-Ashaar?

A battle by the name of "Al-A'shar" was not mentioned. Rather, "Yawm Al-A'shar" (the Day of Tens) was one of the days of the Battle of Al-Buwaib, where Al-Muthanna ibn Harithah led the Muslims. It was named this because every man out of a hundred Muslims killed ten Persians, resulting in the death and drowning of approximately one hundred thousand Persians.