Complex sentence: On 16 August 1931, the first anniversary of his inauguration, Trujillo made the Dominican Party the nation's sole legal political party; however, the country had effectively become a one-party state with Trujillo's swearing-in.
Split into simpler sentences: On 16 August 1931, the first anniversary of his inauguration, Trujillo made the Dominican Party the nation's sole legal political party. However, the country had effectively become a one-party state with Trujillo's swearing-in.