Afghanistan began facing severe economic hardships during the 1970s when neighboring Pakistan, under Zulfikar Ali Bhutto, began closing the Pakistan-Afghanistan border crossings. This move resulted in Afghanistan increasing political and economic ties with its northern neighbor, the powerful Soviet Union of that time. The 1979 Soviet invasion and ensuing civil war destroyed much of the country's limited infrastructure, and disrupted normal patterns of economic activity. Eventually, Afghanistan went from a traditional economy to a centrally planned economy up until 2002 when it was replaced by a free market economy. Gross domestic product has fallen substantially since the 1980s due to disruption of trade and transport as well as loss of labor and capital. Continuing internal strife severely hampered domestic efforts to rebuild the nation or provide ways for the international community to help.