Along with a number of other Cossack commanders, Hosseinpour was a founding member of the new Imperial Iranian Armed Forces during the reign of Reza Shah Pahlavi.

The military force headed by the coup officers left Karaj, a town about 40 km from Tehran, and arrived at the Ghazvin Gate (close to the present Mehrabad International Airport).

Hosseinpour retired from the Imperial Iranian Army at the age of around 60 and spent the rest of his life monitoring the affairs of his villages and estates and engaging in philanthropic activities.

The Iranian government granted the ownership of a number of estates, farms, parcels of land, and villages to him and a few other top commanders in compensation for their fathers' financial losses incurred when they immigrated to Persia.

Hosseinpoor's family received numerous villages, farms, estates, large parcels of land and houses, which Assadollah eventually inherited.

Hosseinpour's grandfather was Amir Hossein, a high ranking commander of Shirvan and a close colleague and friend of Pasha Khan Pashai.

Amir Hossein married the daughter of one of the landlords of Saraband territory in the town of Arak, Iran, all of whose wealth (villages and large parcels of land) was inherited by Hosseinpour as well.

He was buried in Tehran's Baháʼí cemetery (Golestaneh Javid), which was destroyed by Islamic mobs after the Iranian political unrest of 1979 in Iran.