User blog comment:Sasafred12/Suggestions?/@comment-4940710-20120707050325

I have a couple of ideas.

Justinian's Patience

Justinian I opts for the Byzantine Empire to expand gradually, rather than trying to completely restore the Roman Empire's old borders within his lifetime. Justinian could modestly expand the empire by conquering the Vandals, but refrain from trying to take Italy or Spain. He could also try to use diplomacy to lay the groundwork for the eventual integration of the Germanic kingdoms into the Byzantine Empire. In OTL, Justinian's campaigns in Italy and Spain wasted manpower and resources that could have been used to deal with Persia and Slavic invaders in the Balkans, devastated Italy, weakened the Byzantine economy, and were probably a factor in the Byzantine Empire's later decline.

Prussia, the German State that Never Was

Duke Konrad I of Masovia does not invite the Teutonic Order to conquer the Prussians.

In OTL, the Teutonic Knights conquered the Prussians and established the Monastic State of the Teutonic Knights. Over time, the rulers forced the Prussians to convert to Catholicism and Germanized them (the Prussians had previously been Baltic). Then in 1525, Albert of Prussia converted to Lutheranism and transformed the Teutonic state into the Duchy of Prussia. Two and a half centuries thereafter, Prussia, along with Austria and Russia, divided the Polish-Lithuanian Commonwealth between themselves.

Now in OTL, the Old Prussians were attacking Poland because Poland had always been hostile to them. For this timeline to be plausible, it would have to start with an alternate trend of Poland trying to be on amicable terms with the Old Prussians.