Today in 1964, the Gulf of Tonkin Resolution was passed as a joint resolution of the US Congress. Without any formal declaration of war, it was used as the legal authority for an escalation of US involvement in the Vietnam conflict.
1. America keeps her word. Here as elsewhere, we must and shall honor our commitments.
2. The issue is the future of southeast Asia as a whole. A threat to any nation in that region is a threat to all, and a threat to us.
3. Our purpose is peace.. We have no military, political, or territorial ambitions in the area.
4. This is not just a jungle war, but a struggle for freedom on every front of human activity. Our military and economic assistance to South Vietnam and Laos in particular has the purpose of helping these countries to repel aggression and strengthen their independence.
President's message to Congress 5 August 1964
Source: US Congress, Senate, Committee on Foreign Relations, 90th Congress, 1st Session