Two land-locked, desperately poor African countries are gripped by rebellions in the north that have left huge chunks of both nations outside of government control.

The simple answer lies in the vastly different challenges faced by intervention forces. Northern Mali is home to al-Qaida-linked militants who are stocking weapons and possess stores of Russian-made arms from former Malian army bases as well as from the arsenal of toppled Libyan leader Moammar Gadhafi. The local and foreign jihadists there are digging in and training forces in preparation for jihad and to repel an invasion. Central African Republic, by contrast, is dealing with home-grown rebels who are far less organized and have less sophisticated weapons.

The numbers of troops being sent to Central African Republic are relatively small — Republic of Congo, Cameroon and Gabon are each sending about 120 soldiers. The rebels stopped their advances toward the capital on Dec. 29, perhaps at least in part because of the presence of the foreign troops who have threatened to counterattack if the rebels move closer to Bangui, the capital. In Mali, it will take far more than the 3,000 African troops initially proposed for a military operation to be successful in ousting the militants, analysts say.