Although herbicidal warfare uses chemical substances, its main purpose is to disrupt agricultural food production and/or to destroy plants which provide cover or concealment to the enemy. During the Malayan Emergency (1948–1960), the British military deployed herbicides and defoliants in the Malaysian countryside (including crop fields) in order to deprive Malayan National Liberation Army (MNLA) insurgents of cover, potential sources of food and to flush them out of the jungle. Deployment of herbicides and defoliants served the dual purpose of thinning jungle trails to prevent ambushes and destroying crop fields in regions where the MNLA was active to deprive them of potential sources of food. Herbicides and defoliants were also sprayed from Royal Air Force (RAF) aircraft. The use of herbicides as a chemical weapon by the U.S. military during the Vietnam War has left tangible, long-term impacts upon the Vietnamese people and U.S soldiers that handled the chemicals. More than 20% of South Vietnam's forests and 3.2% of its cultivated land were sprayed at least once between during the war. The government of Vietnam says that up to four million people in Vietnam were exposed to the defoliant, and as many as three million people have suffered illness because of Agent Orange, while the Red Cross of Vietnam estimates that up to one million people were disabled or have health problems as a result of exposure to Agent Orange. The United States government has described these figures as unreliable.