So the only two possible alternatives were invading or doing absolutely nothing??

Yes, with a nation like Iraq, with a proven record of military expansionism and construction and use of WMD, in the end those would basically have been the only alternatives, although I would have used the term "military action" to generalize it a little more, and the choice might have come later. But it would have come.

The status quo was not stable. Sanctions were a complete failure, except at hurting the average Iraqi. Saddam was largely ignoring the U.N., except when he was leading them down the primrose path. We can see right now how successful U.N. diplomacy is at disarming Iran. The people tried revolution after the first Gulf War. They died.

Both U.S. inspection teams declared that Saddam was prepared to restart his weapons programs the minute the heat was off.

I hear a lot about alternatives here, mostly along the lines of "there must be SOMETHING." Most people are short on details.