The Afghan conflict is the series of events that have kept Afghanistan in a near-continuous state of armed conflict since the 1970s. Early instability followed the collapse of the Kingdom of Afghanistan in the largely non-violent 1973 coup d'état, which deposed Afghan monarch Mohammad Zahir Shah in absentia, ending his 40-year-long reign. With the concurrent establishment of the Republic of Afghanistan, headed by Mohammad Daoud Khan, the country's relatively peaceful and stable period in modern history came to an end. However, all-out fighting did not erupt until after 1978, when the Saur Revolution violently overthrew Khan's government and established the Democratic Republic of Afghanistan. Subsequent unrest over the radical reforms that were being pushed by the then-ruling People's Democratic Party of Afghanistan (PDPA) led to unprecedented violence, prompting a large-scale pro-PDPA military intervention by the Soviet Union in 1979. In the ensuing Soviet–Afghan War, the anti-Soviet Afghan mujahideen received extensive support from Pakistan, the United States, and Saudi Arabia in a joint covert effort that was dubbed Operation Cyclone.