Rather than SUBTITLE CARDS, Text on screen should be written as SUPER:
SUPER: 1976: Pol Pot becomes Prime Minister of Cambodia after King Sihanouk resigns. He orchestrates one of the worst genocides in history against his own people.
TEXT FADE OUT:
SUPER: 1977: Pol Pot reneges on a peace treaty with Vietnam and sends his Khmer Rouge forces invade to recover Cambodian lands.