Complex sentence: From late 1940 Hitler wanted Belgrade to unequivocally choose sides, and pressure intensified, culminating in the signing of the Tripartite Pact on 25 March 1941.
Split into simpler sentences: From late 1940, Hitler wanted Belgrade to unequivocally choose sides. Pressure intensified, culminating in the signing of the Tripartite Pact on 25 March 1941.