Reign of Terror happened in 1793 after the Radical took control over the leadership positions within the French Revolution. This radicals were led by a man named Maximilien de Robespierre
During this time a lot of people within the French Revolutionaries group believed that the monarch has sent its people to inlingtrate the group. As a result, many of them started to threw around accusations, They arrested the people who they believed to be disloyal to the revolutionary cause even without hard evidence.
As a result, around 40,000 were massacred under Robespierre's leadership. The reign of terror lasted until they removed Robespierre from power on July 1794.
Wilson tried to keep the United States neutral during World War I but ultimately called on Congress to declare war on Germany in 1917. After the war, he helped negotiate a peace treaty that included a plan for the League of Nations.