Final answer:
Key events promoting German unity include the Wartburg festival in 1817, the 1848 Frankfurt Assembly, the Zollverein customs union, and Otto von Bismarck's leadership towards the establishment of the German Empire in 1871.
Step-by-step explanation:
Several key events during the early 1800s promoted German unity. In 1817, German nationalists convened at Wartburg, igniting the flame of national identity with a tricolor flag. This sense of unity was further solidified through the creation of the Germanic Confederation in 1815 as a defense alliance.
The 1848 Frankfurt Assembly, as the first freely elected German parliament, was another significant step towards unity, though its constitution was not ultimately implemented. The establishment of the Zollverein in 1834 under Prussia's leadership also promoted economic unity and strength among German states.
Otto von Bismarck's realpolitik and military victories against Denmark, Austria, and France from 1864 to 1871 played a pivotal role, ultimately leading to the proclamation of the unified German Empire in 1871.