The Hussites were a very effective fighting force. Many new tactics were developed including war wagons. These helped play an important part in winning an independent Czech kingdom after numerous crusades against them. Finally a decisive victory at the Battle of Lipany in 1434 allowed them to finally get peace with King Sigismund in 1436.
The five failed crusades against the Hussites helped to spread their message of reform across Europe. The Church ended overt attempts to destroy them and changed their strategy to isolate the new Czech Kingdom and minimize the spread of what they considered the Hussite Heresy.
The flag above became the official flag of the Hussite armies after the end of the wars. It combined elements from a number of popular flags during the wars.
* * *
Sean Sherman has been a fan of alternate timelines ever since seeing Spock with a goatee. By day he is a CPA, at night he explores the multiverse and shares his findings over at his blog, Other Times.