Complex sentence: In February 1940, Finland's Commander-in-Chief marshal Mannerheim expressed his pessimism about the military situation, prompting the government to start peace negotiations on February 29, the same day the Red Army commenced an attack against Viipuri.
Split into simpler sentences: In February 1940, Finland's Commander-in-Chief marshal Mannerheim expressed his pessimism about the military situation, prompting the government to start peace negotiations on February 29. The same day the Red Army commenced an attack against Viipuri.