• The domino effect is when one domino is pushed down and the rest follow.
• Countries like China, the USSR, and North Vietnam were communist countries.
• Countries like South Vietnam were democratic countries.
• Ho Chi Minh believed that all of Vietnam should be communist.
• Eisenhower, president of the United States, believed that if one country fell to communism, more countries in the area would also fall, just like the domino effect.

EXTENDING THE DISCUSSION
After the observational question, randomly call on one or more students to share what they or their partner answered. Then ask the class, “Did anyone notice…?” using the suggestions above or anything else you’ve noticed.

• Why did the U.S. believe so strongly in the domino theory?
• Did U.S. actions in Vietnam actually stop the spread of communism?
• Why did the theory only hold true for Laos and Cambodia?
• What strategies did the U.S. use to act on the domino theory?
• How did people in other countries respond to the U.S. involvement?

EXTENDING THE DISCUSSION
After students have shared what they notice, ask the class, “Did anyone wonder…?” using the suggestions above or anything else you might think is interesting or relevant to the lesson.

To the observational question, What was the domino theory?

LOW-LEVEL

The domino theory said if one country fell, others would too.

HIGH-LEVEL

The domino theory stated that if one country in a region became communist, nearby countries would also fall under communism like a row of dominoes.

RESPONDING TO RESPONSES
Emphasize and celebrate each student’s use of the key vocabulary to support a culture of “no wrong answers.”