Pan-Germanism was highly influential in German politics in the 19th century during the unification of Germany when the German Empire was proclaimed as a nation-state in 1871 but without Austria (Kleindeutsche Lösung/Lesser Germany), and the first half of the 20th century in the Austro-Hungarian Empire and the German Empire. From the late 19th century, many Pan-Germanist thinkers, since 1891 organized in the Pan-German League, had adopted openly ethnocentric and racist ideologies, and ultimately gave rise to the foreign policy "Heim ins Reich" pursued by Nazi Germany under Austrian-born Adolf Hitler from 1938, one of the primary factors leading to the outbreak of World War II.