Realizing that it is a mistake to take the solution to one military problem and apply it blindly to another, Guajardo carefully created his own plan, selectively using tactics and techniques used at Son Tay. An example was the manner in which the Son Tay raiders used helicopters to neutralize the guard towers in 1970. There, a CH-53 with miniguns on both sides flew between two guard towers, hovered at the same level as the towers, and fired the miniguns directly into them. The wooden guard towers at Son Tay, pulverized by miniguns firing 6,000 7.62mm rounds per minute, were, in effect, sawed off their supports. This allowed the initial assault group to come in and land unhindered in an open space in the compound.
Though Guajardo did not have a helicopter as big as the CH-53, or miniguns for that matter, he could improvise. For aircraft, four Bell 206 helicopters, each with a crew of two and capable of carrying five passengers, would be used. Since the Mexican Army had few helicopters, only the towers in the west and the center would be attacked. These four helicopters and their passengers, code named Group Z because it was staging and launching from Zacatecas, would hit Chinampas first. Coming in from the west, each helicopter would fly directly to its designated target, one of the four towers. Flying nap-of-the-earth, Group Z would use the hills west of Chinampas to mask their approach. Once clear of the hills, the pilots would only have a few seconds to orient themselves and line up on the tower they were to hit, all the while making a final high-speed approach.
The challenge that faced each pilot in Group Z was covering the last few meters of open ground as quickly as possible, clearing the outer wall, then rapidly bringing their helicopter to a hover a few meters away from the tower. With a main blade diameter of 11.3 meters, the closest the Bell 206s could come to the tower, or any other obstacle for that matter, was six to eight meters. That, however, was close enough.
Once the pilot or the co-pilot had brought the helicopter to a hover, the other crewmen, armed with automatic rifles, would fire out of their open windows into the guard tower. Guajardo knew this fire would be wildly inaccurate, especially since the crews would not be permitted to practice before the operation in order to preserve secrecy. But it didn't need to be accurate. Guajardo was counting on the surprise assault from the air, coupled with the suppressive fire from the helicopter crew, to allow the passengers enough time to rappel out of the helicopter onto the ground at the base of the tower.
The passengers carried by the Bell 206s were four teams of combat engineers armed with automatic rifles and a variety of explosives. Each team, consisting of an officer, a sergeant, and three sappers, had been hand-picked by a colonel of the engineers who was a member of the Council of 13. During the assault on Chinampas, while the helicopter hovered and the crew fired on the occupants of the tower, the engineers would exit the helicopter using the speed-rappel technique pioneered by the U.S. Army's special operations helicopter group, Task Force 160.
The nylon rope used was two inches thick and stiff. The engineers, wearing leather gloves, would slide down it like firemen dropping down a fire pole. Since the drop would only be twenty feet, even if someone let go, the chances of severe injury would be minimal. Once on the ground at the base of the towers, the engineers, using explosives, would force their way into the tower and clear it as rapidly as possible using gunfire and explosives.
Unlike the pilots, the engineers were allowed to practice exiting the helicopter and the techniques to be used in clearing the towers. To ensure security, each team in Group Z, along with the helicopter and crew that would transport it, was trained in isolation in a different part of Mexico.
None were told what their actual target was. Instead, the men, even the officers in charge, were told that they were being trained to deal with prison riots. To make this'cover story more convincing, the dummy towers and compounds they drilled on were patterned after actual prisons within the state where they were located. Even with this cover story, all rehearsals were classified top secret. Only on June 29, the day before the actual raid, would all members of Group Z be brought together at an abandoned airfield outside of Zacatecas. There, Guajardo himself would issue the actual order for their real target.
Since there was no way of knowing what helicopters and helicopter crews would be available on the day of the raid, Guajardo, who was not a pilot, decided to keep them out of the mission planning. To protect the security of the operation, Guajardo made it a habit to use different helicopter crews. An Air Force colonel on the council advised Guajardo to include the pilots in the rehearsals, but was rebuffed for his efforts. "This is," Guajardo told him, "a ground operation. All the helicopters are needed for is transportation. And for that, all the pilots need to be given is a course, speed, and destination." Unstated was Guajardo's dislike of aviators, a breed he considered to be overpaid and underworked. So the pilots, like many other participants, would learn of their role at the last minute.
With the two western and two center towers seized or under attack, the door to direct insertion of the main force into the compound itself was open. The open spaces needed to grow the beautiful gardens of Chinampas, which is the name given ancient Aztec floating gardens, provided ample space for helicopters to land within the walls of the fortress. Two assault groups, one coming in from the north and one from the south, would use these open spaces as landing zones.
The assault group coming down from the north, designated Group M for its staging area near Monterrey, was commanded by Major Antonio Caso, Guajardo's deputy commander for this operation. Consisting of two Bell 205 helicopters and twenty-four infantrymen, Group M would land in the northern half of the garden, seize the northern side of the main house, and engage the barracks with automatic rifle, machine gun, and recoilless rifle fire.
Converging on Chinampas from Distrito Federal in the south was Group D. It consisted of twenty-four men transported in two Bell 205A helicopters, nicknamed Hueys by the American military. Guajardo's corn mand group, in a Bell 206 like those used by the engineers, would follow Group D into Chinampas. Consisting of himself, two radiomen, and two riflemen to be used as runners as needed, Guajardo would move along with Group D once on the ground. Landing in the southern half of the garden, this group would seize the southern half of the main house and, from there, engage any of Alamdn's men holed up in the stable or garage.
So as to prevent confusion, the east-west walk in the garden served as a boundary to separate the landing zones and areas of responsibility for groups M and D.
A fourth assault group, Group N, consisting of 24 infantrymen commanded by a lieutenant, would approach from the east. Staging out of Nuevo Dolores, hence its designation "N," this group would not enter Chinampas. Its mission, instead, was to seize the airfield east of Chinampas, clear all buildings there, and capture, or if that was not possible, disable all aircraft on the field. Once this was completed, Group N was to deploy itself on either side of the footbridge, establishing fields of fire so as to prevent anyone from escaping from Chinampas. Though there was concern over the use of so junior an officer to command one of the assault groups, Guajardo dismissed it. The lieutenant, a graduate of the Mexican Military Academy at Chapultepec, was highly recommended by Colonel Molina.