On February 16th, 2010, Mormon forces initiated a major offensive from St. George, Utah toward Las Vegas and Boulder City, Nevada, with the intent of securing Hoover dam and forcing the FRCAF out of Nellis AFB. A brigade-sized Mormon force was dispatched along I-15. With most FRCAF assets grounded for anything but emergencies due to continued fuel shortages, and very little civilian traffic on the now dangerously unpatrolled interstate system, the Mormon brigade was not spotted until it was only miles outside of Las Vegas, at I-15 Exit 64 around 0200 PST on February 17th.
Arizonan forward pickets opted not to engage and immediately withdrew, warning their commanders via radio. FRCAF strike assets were mobilized immediately, but the Arizona National Guard's response, critically, was sluggish.
The Arizonan NG had expected a Mormon attack to first strike Hoover dam and push toward Las Vegas from the east, due to the continued Mormon occupation of Kingman and Dolan Springs, Arizona - some Arizona officers even thought the Mormons would be brazen enough to attempt and amphibious operation across Lake Mead. As a result, the bulk of the Arizonan force in Nevada was dug in around the Hoover Dam area. Only two mechanized infantry companies were held in reserve to the north, encamped near Nellis. Though the National Guard began to reposition its forces almost immediately, Mormon forces were in too close to hold them outside the city. Even as Californian F-15s were finally cleared for takeoff, around 0215, Mormon forces made contact with 1st Battalion, 158th Infantry Regiment of the Arizonan National Guard, just outside Nellis Air Force Base.
Fighting was fierce and quickly became a slow urban slog. Mormon forces were so close to Nellis that FRCAF planes actually had to overfly them and circle back in order to deploy their ordinance. The Mormon Brigade was especially well equipped for a Mormon unit, and was potentially formed around a former Utah National Guard unit - it possessed a wide array of night vision devices, 82mm and 120mm mortars, multiple light and heavy anti tank weapons, (including a limited number of FGM-148 Javelin ATGMs) and upwards of 80 Humvees. At 0240, Mormon troops advancing from North Las Vegas Boulevard breached the Nellis AFB perimeter. 82mm mortars were employed in an attempt to crater Nellis' runways to prevent the escape of the squadron of F-15s stationed at the base - this tactic proved only somewhat effectual, causing only limited damage, but dissuading the pilots from attempting takeoff.
Four Arizonia AH-64D Apache Longbow attack helicopters arrived over Las Vegas around 0300. By this point the National Guard had been pushed back, and Nellis AFB was nearly encircled, but two infantry battalions had been redeployed to Nellis in an attempt to breakthrough. The flight of Apaches attempted to support this effort, but Mormon forces were so entangled with FRCAF security forces and the Arizona NG that they could not engage without endangering friendly troops. As a result they were redirected to a group of Mormon 120mm mortar batteries that had set up in Las Vegas Motor Speedway. They succeeded in destroying 11 of the 16 mortars, and the Apache flight is often credited with preventing the complete encirclement of Nellis.
Nevertheless, Mormon troops totally overwhelmed the outnumbered and unprepared defenders of Nellis, methodically clearing the base building by building, and taking precious few prisoners. Most of the base's aircraft managed to escape, but two F-15Es were downed by Mormon MANPADs while taking off, and a further two were captured. At 0713 the remnants of 1st and 3rd Battalions of the Arizona NG, and the Nellis security force, were withdrawn across Tyndall Avenue into the base housing and commercial complex. All together, they sustained 215 casualties. Accurate Mormon casualty figures are not available, but the Mormons are thought to have lost upwards of 300 men in the assault.
Nellis' fighter force was hastily rebased to Luke Air Force Base in Arizona - arrangements were made to provide additional logistical support to the Arizona Air National Guard to accommodate the presence of the more than 48 fighters.
Meanwhile, Mormon forces to the west of Las Vegas Motor Speedway surged across open ground toward the Nellis Solar Power Plant, with the aim of outflanking the remaining Nellis defenders and seizing the base. By midday the Arizona National Guard had pulled back to the vicinity of Mike O'Callaghan Federal Hospital, and Mormon forces were free to maneuver through the solar farm, and even into Las Vegas proper - no Arizonan on Californian forces were present north of the I-15 until a company of Arizonan guardsmen was deployed near Vandenburg Detention Basin to the northwest of Nellis around 1730.
Mormon forces to the south put pressure on Nellis' remaining defenders by pushing across Tyndall avenue toward the base PX, but simultaneously made a large push to the west across North Nellis Boulevard in an attempt to push to North Las Vegas Boulevard and cut off the 1st and 3rd battalions from exfiltrating via that route, forcing them to withdraw to the north, only to be stopped by the Mormon troops who had pushed through the solar farm and into the base's sprawling housing developments. Nellis was almost entirely under Mormon control by the morning of the 17th.
After the seizure of Nellis, Mormon forces were able to operate in Las Vegas with general impunity - Arizonan and Californian forces were significantly outnumbered, and Mormon troops continued to pour into the area from Utah. The final blow came around 1600, when Mormon troops pushed south through Henderson, and into Boulder City, linking up with Mormon troops from Arizona and securing Hoover Dam. With the dam lost and the Mormons firmly entrenched in Las Vegas, the Arizona National Guard commander ordered a withdrawal to the mining complex at Sloan. Las Vegas was now entirely under Mormon control, at the cost of of over 600 men. battle
The First Battle of Las Vegas had enormous political consequences for the Californian and Arizonan governments. The Mormon assault had left 198 Arizonan troops dead, the single worst loss of life for the Guard since the Vietnam War. The governor of Arizona resigned by the end of the month, replaced by his chief of staff. The Californians, in having lost both the critical aviation facilities at Nellis AFB and Hoover Dam in a matter of hours, along with the F-15 combat losses in history.
However, the battle served to engender more widespread public support for continuation and expansion of the war in both Arizona and the FRC,