Complex sentence: Ulmanis was a Latvian nationalist, who espoused the slogan "Latvia for Latvians" and held that every ethnic community in Latvia should develop its own authentic national culture, instead of assimilating.
Split into simpler sentences: Ulmanis was a Latvian nationalist, who espoused the slogan "Latvia for Latvians". Officially, he held that every ethnic community in Latvia should develop its own authentic national culture, instead of assimilating.