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 conditions, many people died. Thousands more Hmong people, mainly former soldiers and their families, escaped to remote mountain regions - particularly Phou Bia, the highest (and thus least accessible) mountain peak in Laos. At first, these loosely organized groups staged attacks against Pathet Lao and Vietnamese troops. Others remained in hiding to avoid conflict. Initial military successes by these small bands led to military counter-attacks by government forces, including aerial bombing and heavy artillery, as well as the use of defoliants and chemical weapons.