Frederick the Great took Silesia from Austria without warning sparking war. In the Seven Years' War Prussia occupied and thoroughly plundered Saxony and Saxony was a forced Prussian ally in 1806. Interestingly, Napoleon was urged in 1813 in Saxony to undertake an operation similar to what Wellington and the Portuguese did while retreating to Lisbon and the Lines of Torres Vedras. Napoleon refused as he deemed it dishonorable to do that to an ally.