Well tour, far be it from me to correct you on Constitutional matters, but Article 8, section 11 calls for the Congress (not the Senate acting alone) to declare war.
This is what was done on December 8, 1941.
But in 1951, Harry S Truman went into Korea under the aegis of the United Nations, calling it a "police action". Unless I am mistaken, there have been no formal Congressional declarations of war since.
However, Congress holds the purse strings, and if they don't provide money for any given military activity, it will wither on the vine.
Well, you don't have to go far to feel free to correct me if I'm wrong on something. Having dug out and checked my copy of the Constitution, you are absolutely right: it only says that Congress is empowered to declare war, not that only the Senate has that power.
The question still remains why Congress hasn't been asked to declare war.
Tuor