The Fall of Virgil refers to the 2 January 2737 SEY invasion of the Virgil system by the Vanduul directly after the conclusion of the Siege of Tiber. United Empire of Earth (UEE) forces, depleted after four years of battle, were unable to mount a suitable defense against the invading Vanduul, who pursued them once Tiber fell. Although the system was lost, the UEE Navy was able to cover the retreat of over one million refugees.

Before 2681 and the events of Vanduul-Human First Contact, the Virgil system was on an upward trajectory. As the launchpoint of Project Far Star, it was both a hub for explorers and a symbol of the UEE's continual outward expansion. Cyrene (Virgil I) was growing to be an economic powerhouse, having both a thriving resort industry due to its beautiful, lush landscapes and a robust agricultural system fed by highly fertile soil. However, when the Vanduul began launching regular raids in Virgil, the system's growth slowed. Project Far Star and talks of Senatorial recognition for Cyrene were put on hold pending resolution of the worsening Vanduul-Human conflict.

After the Orion system fell to the Vanduul in 2712, the military forces stationed there retreated into the Tiber system, where they set up a line of defense in anticipation of a forthcoming assault. With the mounting threat to its neighboring systems, Virgil's already faltering tourism industry collapsed, and the system was soon transformed into a military outpost.

At the start of the Siege of Tiber in 2732, the population of Cyrene dropped to a few million people as all those with the means to do so fled. Countless others who did not have the resources to escape on their own applied to the government to help them relocate, but the Imperator Galor Messer IX refused to grant any aid, stating that Cyrene could not afford to lose more workers. Many turned to smugglers to help them flee, but some remained behind, believing that the might of the UEE would eventually prevail. Their faith appeared on the verge of paying off in November 2736, when the UEE conducted a bombing run on Tiber II and destroyed all Vanduul encampments there, enabling them to retake the planet, the Tiber belt alpha, and the Vector-Tiber jump point. Two UEE Navy Battle Groups departed the system for repairs, and two more remained to pick off the few remaining Vanduul. It seemed that the UEE was on the verge of victory.

On 29 December 2736, the tide abruptly turned. A Kingship accompanied by an enormous Vanduul Clan entered Tiber through the Orion-Tiber jump point and opened fire on the 81st Battle Group. Within half a day, three quarters of their ships were destroyed. Admiral Mira Triolo ordered them to retreat into Virgil while she remained behind with the 6th Battle Group to hold the line.

When the remains of the 81st entered Virgil it set off a panic. Millions of people who remained in the system clamored to be evacuated ahead of a potential Vanduul invasion. Citing the actions of the Vanduul in the aftermath of the Battle of Orion, the Governors Council of Cyrene issued a statement assuring the public that a secondary invasion was unlikely to occur, and that they had sent a message to the Imperator requesting immediate military assistance. This helped calm things enough to avoid the threat of riots while the Council, with the help of the 81st, was able to organize an evacuation effort that succeeded in transporting over one million evacuees through the Vega and Oberon jump points over three standard days.

On 2 January 2737 the 6th Battle Group in Tiber fell. Within hours, the Kingship and its accompanying Clan entered the Virgil system headed straight for Cyrene, making landfall at the city of Kastak and launching an all-out assault on the planet. The remnants of the 81st could offer little resistance, but elected to do all they could to hold off the Vanduul while the last transports fled the system under the protection of Squadron 214. When the final transport made it through the Vega jump point, Squadron 214 turned back to attempt to rescue more people. They were able to complete two more runs before they were unable to continue.

The Vanduul continued their assault against Cyrene and the rest of the system unabated until no other life remained. The surface of Cyrene was reduced to nothing, casting a cloud of radioactive ash into the atmosphere that created nuclear winter. Hundreds of thousands of Humans and Tevarin that were unable to escape perished. Those who had not died during the initial Vanduul onslaught soon starved or succumbed to radiation poisoning.

The military aid that the Governors Council of Cyrene had requested did not arrive until well over a week later. By that point, the Virgil system was completely overrun. Instead of entering the system and ousting the Vanduul, the military created a defensive line around the jump point to Virgil in anticipation of another assault. As with the loss of the Orion system, the attack did not immediately occur, and the Vanduul began to harvest Virgil's resources. Multiple scouting missions came back with reports that Cyrene was irrecoverable. In 2743, the UEE announced that they would not retake the system.

Suddenly finding themselves on the front line, residents of the neighboring Vega system took what happened in Virgil as a cautionary tale and began to flee in droves, severely impacting the system's economy. Evacuees from Virgil, most of whom had little in their possession but their clothing, suffered food shortages as they awaited resettlement. Some were able to relocate to other systems, but the majority stayed near the military bases on Aremis (Vega II) and took any jobs that they could. Historians believe that this may have prevented the system's economy from entering a true depression, though it did not avert a recession. Today, over a quarter of people born in the Vega system can trace their lineage back to former residents of Cyrene.

The destruction of the Virgil system deeply affected the UEE. While Orion's loss had been significant, it was a young colony and had not undergone significant development, and Tiber was a sparsely-populated mining system with only small settlements. Virgil had over 300 years of history and was a major system with a world on the verge of recognition. As the heart of Project Far Star, it was also a symbol of the UEE's continual expansion. The UEE Navy's defeat at Tiber and subsequent failure to protect Virgil shook the people's confidence in the military and in the UEE at large. Historians cite the Fall of Virgil one of the many motivating factors that eventually led to the anti-Messer revolution in 2792.