The Northern Alliance is, well, an alliance of northern warlords, warlords and rebels in the West and the government (sort of in exile) led by  Burhanuddin Rabbani. This government is the one recognized by the UN, but was tossed out of Kabul by the Taliban in 1996. The Northern Alliance is held together primarily because of ethnic differences. The northern tribes (Tajiks, Uzbeks and other Turkish groups) fight mainly to avoid domination by the Pushtuns (with or without the Taliban). While the Northern Alliance is an Afghan force fighting the Taliban, and is now taking aid from the United States, it is uncertain if the Northern Alliance could seize control of the entire country, and then hold onto it. The Northern Alliance has signed an agreement with the former king to help put together new national government. The king is a Pushtun who speaks the Afghan dialect of Iranian. But all these plans depend on who controls Kabul and most of the rest of the nation. Short of fuel (to move troops to troublespots) and facing increasing defections, the Taliban is losing control over much of Afghanistan. But, so far, that simply leaves much of the country under no central control