During the civil war, and the ensuing Soviet–Afghan War, most of the countrys infrastructure was destroyed, and normal patterns of economic activity were disrupted. The gross national product (GNP) fell substantially during Karmals rule because of the conflict; trade and transport were disrupted along with the loss of labor and capital. In 1981 the Afghan GDP stood at 154.3 billion Afghan afghanis, a drop from 159,7 billion in 1978. GNP per capita decreased from 7,370 in 1978 to 6,852 in 1981. The most dominant form of economic activity was the Agriculture in Afghanistan. Agriculture accounted for 63 percent of gross domestic product (GDP) in 1981; 56 percent of the labour force worked in agriculture in 1982. Industry accounted for 21 percent of GDP in 1982, and employed 10 percent of the labour force. All industrial enterprises were government-owned. The service sector, the smallest of the three, accounted for 10 percent of GDP in 1981, and employed an estimated one-third of the labour force. The balance of payments, which had improved in the pre-communist administration of Muhammad Daoud Khan; the surplus decreased and became a deficit by 1982, which reached minus $US70.3 million. The only economic activity that grew substantially during Karmals rule was export and import.. What caused the GNP to fall under Karmal?