By 1975, as a result of the collapse of South Vietnam at the end of the Vietnam War and the loss of American support, the Pathet Lao was able to take control of the Laotian government in December of that year, abolish the constitutional monarchy which controlled it and establish a Marxist-Leninist state which is called the Lao People's Democratic Republic. Hmong people, especially those Hmong who had fought against the Pathet Lao, were singled out for retribution. Of those Hmong people who remained in Laos, over 30,000 were sent to re-education camps as political prisoners where they served indeterminate, sometimes life sentences. Enduring hard physical labor and difficult living conditions, many Hmong people died. Thousands of other Hmong people, mainly former soldiers and their families, escaped to remote mountain regions - particularly to Phou Bia, the highest (and thus the least accessible) mountain peak in Laos. At first, these loosely organized groups staged attacks against the Pathet Lao and Vietnamese troops. Other groups remained in hiding in order to avoid conflict. Initial military successes by these small bands led to military counter-attacks by government forces, including aerial bombing raids and the use of heavy artillery, as well as the use of defoliants and chemical weapons.