South African police on their way to El Fasher, Darfur

Forty-two South African Police Service members were due to arrive in El Fasher, Darfur for peacekeeping operations on Monday, reported Sapa March 20, 2006:

The group consisting of 33 men and nine women left for Darfur on Sunday night. Police spokesperson Peter Mbelengwa said they would be deployed in the region for six months as part of the African Union peacekeeping mission.

"They will monitor the service of the police of the Government of Sudan to the community, facilitate the building of good relations between the police and the community, give technical advice and share their experience on the successful adoption and implementation of community policing," said Mbelengwa.

They are the sixth group of police officials to be deployed in Sudan and would relieve members who have served their six months in the country. The SAPS have 125 members deployed in Sudan as part of the AU mission. - Sapa

Note they are replacing police officials on duty in Darfur, they are not in addition to AU forces already serving in Darfur. Why can't they all stay?