On 17 December 1989 the national command authority (NCA) directed the Joint Chiefs of Staff (JCS) to execute PLAN 90-2. JTFSO received the JCS execute order on 18 Dec with a D-Day and H-Hour of 20 Dec 0100 local. The operation was conducted as a campaign with limited military objectives. JTFSO objectives in PLAN 90-2 were to:
A. Protect U.S. lives and key sites and facilities.
B. Capture and deliver Noriega to competent authority.
C. Neutralize PDF forces.
D. Neutralize PDF command and control.
E. Support establishment of a U.S.-recognized government in Panama.
F. Restructure the PDF.
At Forts Bragg, Benning, and Stewart, D-Day forces were alerted, marshaled, and launched on a fleet of 148 aircraft. Units from the 75th Ranger Regiment and 82d Airborne Division conducted airborne assaults to strike key objectives at Rio Hato, and Torrijos/Tocumen airports.
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.
As the lead headquarters for SAC's tanker support, the Eighth Air Force tasked, executed, and directed 144 missions to refuel 229 receivers with over 12 million pounds of fuel. According to General Colin Powell, Chairman of the Joint Chiefs of Staff, the Eighth’s "air refuelers did not just make a difference in this operation -- they made it possible." This mission introduced the F-117A Stealth Fighter to combat for the first time.
Air National Guard units participated in the operation because of their regularly scheduled presence in Panama for Operations CORONET COVE and VOLANT OAK. Only Pennsylvania's 193d Special Operations Group (SOG) was part of the integral planning process by the Joint Chiefs of Staff and the Air Staff for the invasion of Panama. The 105th Military Airlift Group (MAG) and the 172 MAG provided airlift support for the operation. They flew 35 missions, completed 138 sorties, moved 1,911 passengers and 1,404.7 tons of cargo which expended 434.6 flying hours. ANG VOLANT OAK C-130 aircrews flew 22 missions, completed 181 sorties, moved 3,107 passengers and 551.3 tons of cargo, which expended 140.1 flying hours. The ANG CORONET COVE units, the 114th TFG and the 18Oth TFG flew 34 missions, completed 34 sorties, expended 71.7 flying hours and expended 2,715 rounds of ordnance.
Urban terrain provides high potential for fratricide because of the likelihood of close quarters (high weapons density), recognition problems, and unfamiliar secondary effects of weapons. During Operation JUST CAUSE soldiers employed several ineffective and dangerous techniques to breach various fences, walls, and barred doors with grenades, rifle fire, and even anti-tank weapons. Direct fire support, even from just a block away, is very difficult to control. During JUST CAUSE mechanized forces providing fire support were told by brigade a light force had cleared a tall hotel building only to the second floor. In actual fact, it had cleared to the tenth floor and was fighting in a counter-sniper engagement. Seeing this fire and apparently some weapons protruding, the mechanized forces began to suppress. This drew return fire from the friendly light force for some seconds before coming under control. The extensive destruction of civilian housing seen by TV viewers around the world resulted rather from a style of fighting that is based on abundant firepower.
The high casualties and use of resources usually associated with all-out urban warfare did not occur. The United States suffered 23 KIA and 324 WIA, with estimated enemy casualties around 450. There were an estimated 200 to 300 Panamanian civilian fatalities. Some were killed by the PDF, others inadvertently by US troops. More civilians almost certainly would have been killed or wounded had it not been for the discipline of the American forces and their stringent rules of engagement (ROE). However, the United Nations (UN) put the civilian death toll at 500; the Central American Human Rights Defense Commission (CODEHUCA) and the Peace and Justice Service of Panama both claimed between 2,000 to 3000; the Panamanian National Human Rights Commission and an independent inquiry by former Attorney- General Ramsey Clark claimed over 4,000. Thousands were injured. As it turned out, the figure of Panamanian dead was large enough to stimulate debate over the need for the invasion to remove Noriega, but not large enough to generate a sense of outrage in Panama or abroad, or to turn the Panamanian people against the US intervention or the nation-building program that followed it.
The US troops involved in Operation Just Cause achieved their primary objectives quickly, and troop withdrawal began on December 27. Noreiga eventually surrendered to US authorities voluntarily.
Operation JUST CAUSE was unique in the history of U.S. warfare for many reasons. As the largest single contingency operation since World War II, it focused on a combination of rapid deployment of critical combat power and precise utilization of forward deployed and in-country forces. Impressed by the smooth execution of JUST CAUSE, General Stiner later claimed that the operation was relatively error free, confining the Air-and Battle doctrine and validating the strategic direction of the military. He concluded, therefore, that while old lessons were confirmed, there were "no [new] lessons learned" during the campaign. Despite Stiner's assertions, Operation JUST CAUSE offers important insights into the role of force in the post Cold War period and the successful conduct of a peacetime contingency operation.