Why did African Union troops enter Anjouan in 2008?

In 2008, African Union and Comorian troops invaded the island of Anjouan to resolve a political impasse caused by the island's leader, Col. Mohamed Bacar.

The conflict began in 2007 when the federal government, citing violence and voter intimidation, ordered the Anjouan government to postpone local presidential elections and demanded that Bacar step down. Bacar defied these orders and held an election in June 2007, declaring himself the winner. Because the federal government and the African Union refused to recognize these results and demanded new elections—which Bacar refused to hold—the African Union imposed sanctions on his administration. When these sanctions failed to force compliance, the military intervention was launched on March 25, 2008, to secure the island and remove Bacar from power.1