Answer:
The attack on Pearl Harbor.
Step-by-step explanation:
The given speech is quoted from the "Infamy Speech" given by President Franklin D. Roosevelt in 1941 after the unprovoked attack by the Empire of Japan on the United States' military base in Pearl Harbor. This speech also signals the involvement of the United States into the Second World War.
The surprise attack on the United States by the Japanese troops even while still in conversation with each other led to the "immediate' declaration of war on Japan by the US. This further propels the nation to be involved in the Second World war, and also signals an end in the US-Japan relationship.