Excerpts from Books and Wikipedia
"Alexander's greatest achievement was his victory over Napoleon, who had attacked Russia in 1812, and marched with his Grande Armée from France to Moscow, but was then expelled from Russia and later defeated by a coalition of allies, Russia among them. Over the course of a number of diplomatic congresses, the victorious Tsar played an impressive role in determining the political restructuring of post-Napoleonic Europe. . . . During the second half of his reign, Alexander became increasingly arbitrary, reactionary, and fearful of plots against him; as a result he ended many of the reforms he made earlier. He purged schools of foreign teachers, as education became more religiously driven as well as politically conservative. . . . Alexander died of typhus in December 1825 while on a trip to southern Russia. He left no children, as his two daughters died in childhood. Neither of his brothers wanted to become emperor. After a period of great confusion (that presaged the failed Decembrist revolt of liberal army officers in the weeks after his death), he was succeeded by his younger brother, Nicholas I." [Wikipedia]