Main idea: Cultural hearths promoted by the spread of new ideas, practices, and technology in different parts of the world.
Answer:
President Kennedy contributed to America during the Cold War era because he pretty much prevented another World War. This is because America found out that the Soviet Union sent missiles to Cuba and they starting panicking because they were extremely vulnerable to the Soviet missiles. Kennedy set up the armed forces to attack Cuba sparking ww3, but that was canceled because Krushov (or however you spell it) told Kennedy to remove their missiles from Turkey and they'll remove theirs from Cuba. And so they agreed and withdrawn their missiles.
Also, two tanks at the Berlin Wall were at a stand-off, ready to shoot tank explosions at each other. Luckily, Kennedy called Krushov (or however you spell it), to move their tanks back a few feet and they'll do the same, so they kept going until the tanks decided to go back.
You're welcome
Explanation:
1. The Pax Mongolica (1 century of peace w/ neighboring people under mongol rule)
2. Unifaction of Russia
3. The Pax Mongolica reopened of silk road routes from Asia to Europe
