Excerpts from Books and Wikipedia
"His own assassination marked the epoch event for the Crisis of the Third Century—nearly 50 years of civil wars, foreign invasion, and collapse of the monetary economy, though this last part is now disputed. . . . As emperor, Alexander's peacetime reign was prosperous. However, Rome was militarily confronted with the rising Sassanid Empire and growing incursions from the tribes of Germania. He managed to check the threat of the Sassanids. But when campaigning against Germanic tribes, Alexander attempted to bring peace by engaging in diplomacy and bribery. This alienated many in the Roman Army and led to a conspiracy to assassinate and replace him." [Wikipedia]