The Reformation had begun in Germany in the 1500s. By the end of the movement, a significant number of German states had converted to Protestantism.

This led to a major barrier to unification in the 1800s:

• as the most recent protectors of the Holy Roman Empire, the Austrians had remained Catholic
• Austria held great influence over the more southerly German states - they too remained Catholic
• Protestantism had originated and remained in the northern German states
• Prussia was Protestant - as were the northern states it most influenced

This religious schism meant that unification would be difficult to bring about.