Nigeria's vast oil wealth, a population that includes one in every five Africans and a willingness to wade into regional turmoil have made the country a power in West Africa and a political force across the continent.

"When there are crises, the countries have looked upon Nigeria to be an arbitrator," said Ngozi Okonjo-Iweala, the former Nigerian minister of finance and foreign affairs. "It has always been like that. If you are the older brother, the stronger brother or sister, you have to help those who come after you. It is engrained in our cultural approach."

Focusing its foreign policy on African affairs, Nigeria has deployed troops on peacekeeping missions to calm conflicts, sent diplomats to negotiate political disputes and committed resources to organizations that promote development and economic cooperation between African countries.

Nigeria is the region's largest economy representing 55 percent of West Africa's gross domestic product, the most populous nation on the continent at an estimated 130 million people and the continent's largest oil producer.

"They're the big guy on the block in every way," said Princeton Lyman, a former U.S. ambassador to Nigeria and a fellow at the Council on Foreign Relations.

This heavyweight status puts Nigeria in a natural leadership role, one that both its democratically elected and military leaders have embraced since gaining independence from Britain in 1960.

Joining with other newly independent African countries, Nigeria helped found the Organization for African Unity in 1963 to promote African independence and solidarity. The OAU became the African Union in 2001. 

Along with South Africa, the continent's other superpower, Nigeria commands a broad influence within the AU. From May 2004 to September 2005, Nigeria's President Olesegun Obasanjo served as the AU chairman. The AU Force Commander Maj. Gen. Collins Ihekire is Nigerian, and many of the union's peacekeepers come from Nigeria. Abuja, Nigeria's capitol, has been the site of peace talks between the Sudanese government and the rebel groups in Darfur.

Nigeria also played a pivotal role in founding the Economic Community of West African States, or ECOWAS, in 1975 as a regional economic organization of 15 member countries.

From the trade-based foundation of ECOWAS originated the Economic Community of West African States Monitoring Group, or ECOMOG, to unite the region's armies to contain the civil war that erupted in Liberia in the early 1990s.

Nigeria contributed significant financial backing, troops and resources that made  ECOMOG's creation possible. From 1990 to 1997, Nigeria troops made up 12,000 of the organization's white helmets. As the war spilled over the border to Sierra Leone, ECOMOG sent troops in 1998 to push back attacking rebels until United Nations forces arrived.

Liberia's war ended in 2003 and the country's president, Charles Taylor, entered exile in Nigeria as one of the conditions.  In 2006, Obasanjo transferred Taylor to a war crimes tribunal in Sierra Leone to stand trial for his role in the civil war.

Nigerian forces are present in all of the United Nations peacekeeping missions in Africa: Cote D'Ivoire, Sudan, Ethiopia, Eritrea, the Democratic Republic of the Congo and Western Sahara. In total, Nigeria commits 2,462 soldiers to U.N. missions across the globe, according to the United Nations.

In 2005, however, 11 Nigerian police officers of the U.N. mission in Congo were suspended after they were found responsible for sexual misconduct.

Though Nigeria has years of experience securing peace in other countries with the help of outside training and resources, its military may be better equipped to handle operations in other countries than to suppress conflicts within its own borders, according to Lyman.

The Nigerian military has failed to curb an uprising in the Niger Delta region that threatens to shut down the region's lucrative oil industry, either because of a lack of resources or willingness by Obasanjo's government.

Peacekeeping remains the cornerstone of Nigeria's regional influence but the relatively wealthy nation exerts an economic influence on the region as well. 

Nigeria is the only country to set up a trust fund in the African Development Bank for poorer countries to borrow money. After drafting economic reforms within its own borders, Nigerian leaders helped policy makers in other countries with their own reforms.

The Nigerian government also organized and finances a program to send doctors, lawyers, teachers and other professionals to work in other countries.

Obasanjo played an instrumental role in creating the New Partnership for Africa's Development by encouraging other heads of state to create a continent-wide strategy for development.

He also has promoted Nigeria's role on the international stage, not only as one of Africa's leading countries, but as a one of the most populous countries in the world.

Despite this role as a leader and peacekeeper, Nigeria is not completely free of conflict with its neighbors. In 2006, it settled a long-standing border dispute with Cameroon over the Bakassi Peninsula and agreed to withdraw its troops from the area as part of an agreement arranged by the International Court of Justice in 2002.

Nigeria's neighbors may be wary of its power, but on the whole, they respect and appreciate Nigeria's status as a leader, said Okonjo-Iweala.

-- By Anna Shoup, Online NewsHour