This is the reason why the history of HP is the history of Punjab as well.
Religion too shows the same trend.
The Kangra valley has seen countless fanatical turbulences since the pre-historic and mythological times. Nearly the entire state was dominated by Aryans in the beginning, the rest being tribal or aboriginal. Nahan, the Sutlej Valley, Sangla Valley, Sarahan, Kinnaur, Kalpa, Kangra Valley, Mandi and Kullu Valley are great Hindu pilgrim centres. The towns close the Nepal and Tibet began as great Buddhist centres and continue to be so today. Dharamsala has been transformed by the exiled Dalai Lama of Tibet into the Lhasa of India.