The CIA World Fact Book has this to say about Nigeria:

Nigeria is Africa’s most populous country. Formerly under British rule, they attained autonomy in 1960, but were under military rule until a transition to a new constitution in 1999. The longstanding ethnic and religious tensions have resulted in recent elections marred by significant irregularities and violence.  Adding to the stress in this oil-rich country, has been political instability, corruption, inadequate infrastructure, and poor macroeconomic management.

Enter the Ardills.  Bill was born in Nigeria, where his parents were missionaries with SIM (Serving in Mission) for 17 years.  After completing medical school and a surgery residency, Bill went to use his skill in Liberia as an SIM missionary in 1986. 

Meanwhile, God was prepping Dorothy for her own impact as she completed her degree in Medical Technology and then Masters in Missions. While working at Moody Bible Institute, a short-term trip to Liberia resulted in her meeting Bill. They were married in 1987, and continued in Liberia until civil war caused their evacuation in 1990.  In 1992, they were re-assigned to Evangel Hospital in Jos, Nigeria.