Corneria, the fourth planet of the Lylat system, is a fertile farming world with a variety of climates and terrains, more than the vast majority of planets in the Lylat System. It is the homeworld of the Cornerians. Many of the inhabitants live in the shelter of the mountain ranges, where very productive farming soil can be found.
Corneria is currently home to an estimated 85% of the total sentient population of the Lylat system but, due to careful planning, remains a verdant garden world. Its cities and industry were built while keeping in harmony with nature, allowing its rich ecosystem to flourish. It is implied from Star Fox Assault that some military bases might be Cornerian-made islands. Roads on Corneria seem to be built above the ground as to allow the plant life to thrive, and from space the planet looks to have a large amount of cloud cover and oceans. It is the center of culture and government of the Lylat system, and is a prime target for those seeking conquest over the galaxy.
Despite the relatively peaceful nature of its citizens, Corneria has always been a prime target for attack. In earlier times, the original Star Fox team, led by James McCloud, protected the world as mercenaries, with the help of the Cornerian Army. After James' apparent death, the renegade Andross struck against Corneria without warning after amassing an impressively large army. Due to the fact that a war from space had essentially never been waged on the planet before, and the fact that the military forces of the planet were small because the need for them had seemed absent, the Cornerian Army was largely unprepared for the attack. Thus, the army was unable to defend Lylat on its own. The responsibility then fell upon General Pepper to contact the new Star Fox team led by James' son, Fox McCloud, to intervene and save the Lylat system. Vanguard forces of the Venomian Army breached Corneria's defenses, but their advance through an old Cornerian military base was halted by the Star Fox team. Andross' forces were defeated on Corneria, saving the planet from further destruction.
The people of Corneria spent the next few years recovering and rebuilding, attempting the bring the planet back to its former glory. Several cites were hit hard by the attack, some being totally demolished. Roads had to be rebuilt and oceans had to be cleaned, among other things. Andross' forces, in all likelihood, fled the planet after Andross was defeated.
Nine years passed after the Lylat Wars before the crisis involving the Aparoids, which was a completely different scenario. Striking in vast numbers with superior firepower, the Cornerian Defense Force took many casualties. The crazed aliens were able to rush past the planet's defenses and go planetside within minutes of the attack. The problem was worsened by the fact that the Aparoids could control any soldier they came in contact with. In addition, General Pepper eventually went missing: In actuality, he ended up infected by the Aparoids. When Fox arrived on the planet to retake it from the Aparoids, he was so shocked at the events that he even initially wondered whether it actually was Corneria before proceeding with his mission. With air support from the rest of the team, Fox was able to destroy several of the alien radar jammers that disrupted the Arwings' sensor systems, making it hard for them to tell the difference between friend or foe. When Fox's demise was at hand, he was saved at the last minute by his rival, Wolf O'Donnell. Armed with a plasma cannon and riding on the wing of the Wolfen, Fox was able to destroy the majority of the Aparoid forces, including those that had possessed General Pepper and his flagship.
The Beltino Orbital Gate directly above Corneria was the next target of the Aparoid attack. The leftover members of the Cornerian Defense Force and the Cornerian Army, in concert with the Star Fox team, held off the attacking aliens and missiles while the Science Division, headed by Slippy Toad's father Beltino Toad, worked on the Self-Destruct program. This program was literally a "bomb" which could be used to wipe out all of the Aparoid forces after being injected into the Aparoid Queen.
The ending revealed that the sudden strike from the Aparoids left the planet heavily damaged, and that the population suffered, though the individuals who had the time would presumably have retreated into the caves for safety. Due to the unexpectedness of the attack, however, the Aparoids were able to do a massive amount of damage in their short time on the planet. Fortunately, the residential areas suffered the least damage with attacks being aimed mostly at military island outposts. According to the post-war briefing, Corneria's destruction level was an A+, and the Aparoids were expunged. After the war, the Beltino Orbital Gate becomes the center of government for Corneria while the planet is being rebuilt from the invasion. The time of peace that followed was at first somewhat chaotic, with the people of the planet doing their best to recover quickly from the damages.