The place was Panama, the dictator Manuel Noriega, the time was twenty years ago, and the invasion was called Operation Just Cause:
On December 20, 1989, the 82d Airborne Division conducted their first combat jump since World War II onto Torrijos International Airport, Panama. The 1st Brigade task force made up of the 1st and 2nd Battalions, 504th Parachute Infantry Regiment, parachuted into combat for the first time since World War II. In Panama, the paratroopers were joined on the ground by 3rd Battalion, 504th Parachute Infantry Regiment which was already in Panama. After the night combat jump and seizure of the airport, the 82nd conducted follow-on combat air assault missions in Panama City and the surrounding areas.
They were followed later by the 2d and 1st Bdes, 7th Inf Div (L), while the in-place forces comprised of the 3d Bde (-), 7th Inf Div (L); 193d Infantry Brigade (L) and 4-6 Inf, 5th Inf Div (M), assaulted objectives in both Panama City and on the Atlantic side of the Canal. By the first day, all D-Day objectives were secured. As initial forces moved to new objectives, follow-on forces from 7th Inf Div (L) moved into the western areas of Panama and into Panama City.
It was not, in fact, unreasonable for us to think in 2003 that an unpopular and bloody dictator in Iraq could be overthrown, with the state taken over by more friendly elements, and the enemy incapable of fighting an insurgency.
We were wrong about that because of the strength of the Baathist organization, the potential of the pipeline of jihadis (from before the war) that ran through Damascus to Iraq, the vast amount of ammunition and money inside Iraq available to the enemy, the determination of Iran and Syria to fight us after the invasion, and the ruthlessness of the Baathists to stage an insurgency and terror campaign.
In Iraq, our cause was as just. But our assumptions proved wrong. But we still won.
UPDATE: And I should note that our assumptions weren't nearly as fatal to our war effort as Saddam's were when he based his actions on the near-war of Operation Desert Fox carried out 11 years ago this month:
Likewise, the 2004 ISG report stated that in 2003 Saddam discounted the threat of an American-led invasion and considered the air attacks associated with DESERT FOX as the “worst he could expect from Western military pressure.”
And this calls into question whether we could have leveraged our miiltary deployments into coercing Saddam into making real concessions to verify his disarmament under UN Security Council resolutions rather than going to war.