The West African nation of Liberia has been tormented since 1989 by civil war, and the United States, given our long American relationship with it, has a vital interest in its fate.
It's a relationship that began when American slaves were returned to Liberia in 1822. Peacemaking and peacekeeping efforts there have largely been in the hands of regional states, under the aegis of the Economic Community of West African States, spearheaded by Nigerian forces.
The approach was logical: Let the neighbors deal with the problem, a regional solution to a regional problem not unlike the rational approach to the threat of North Korea. Difficulties with that course came from the fact that Liberia's neighbors - Sierra Leone, Ivory Coast, Guinea, Burkina Faso, and Nigeria, all members of ECOWAS - quickly became involved in the Liberian civil conflict themselves.
They backed one Liberian faction or another and, perhaps worse, became deeply involved in commercial ventures. Liberia has resources that include iron ore, diamonds, gold, rubber, and hardwood, trade in which can be very profitable.
Commercial involvement in a country where one is ostensibly making or keeping peace among contesting elements automatically destroys credibility and, ultimately, the ability to be effective. A country whose troops are dealing drugs and diamonds ends up with no credibility.
Now, enter Pakistan, as part of a United Nations peacekeeping force. The Pakistanis had a generally bad experience in the early days of U.N. involvement in Somalia, to the degree that American forces ultimately had to go in to save their bacon.
In general, however, Pakistani forces are competent, well-disciplined, reasonably well equipped, and rather good at peacekeeping. They are a serious force; they are not trigger-happy.
The best part of Pakistani involvement from the U.S. point of view is that, if such competent troops are on the ground, the United States does not have to feel obligated to put its own forces in Liberia.
With American soldiers spread thin across other battle zones, that is good news indeed.