The First, Second, Third, Fouth, Fifth, Sixth, Seventh, Eight, Ninth, Tenth, Eleventh (and maybe even more) Battles of Earth

It is commonly known throughout the Galaxy that Earth, ther homeworld of the Humans, has experienced more than its fair share of battles during the League's long history. Listed here are merely some of the known battles of Earth, in no particular order, followed by an attempt at a chronological categorisation of the different Battles of Earth with more of a description on each one.

Therefore, in no particular order, there is: And possibly many, many others. Sheesh, its a wonder Humanity has lasted this long...
 * The first and second Battles of Earth during the Human-Covenant War
 * The Battle of Earth during the Dalek Civil War
 * The Battle of Earth during the Reaper War
 * The Battle of Earth during the Cybertronian Civil War
 * The Battle of Earth during the Dalek-Cyberman War
 * The Battle of Earth during the Human-Sontaran 'War'
 * The Battle of Earth during the Fall of Lord Hood
 * The Battle of Earth during the Cyberman-Borg War
 * The Battle of Earth during the Human-Klingon War
 * The Battle of Earth during the Second Galactic War
 * The Battle of Earth waged by the Exterminator.

Why Earth?
It has long been debated amongst League historians as to why Earth in particular is such a magnet for alien invasions, battles, and potentially universe-ending events. Many suggest that it is due to Earth's status as a lush, varied world with many resources, and others suggest that there is something about the Human race that many races simply do not like.

World Wars
The first two known Battles of Earth were as a result of Human infighting, rather than external alien interference. World War I and World War II occured in relatively close promimity to each other, lasting from 1914-1918 PLF and 1939-1945 PLF respectively. Both wars concluded with a victory for Western Capitalist nations over Fascist and/or Communist nations, and the United Nations was formed as a result, which would later go on to form important organisations that would play an important role in Humanity's re-intergration into the League, such as UNIT and the UNSC.

The Dalek Civil War
Whilst not affecting the entire planet, merely one city in one nation, the Battle of Earth during the Dalek Civil War in 1963 PLF had the potential to destroy the entire planet through a Time Lord device that both factions of Daleks wanted to claim. UNIT covered up the incident and the existence of the Daleks was kept from the general public, for the time being. Both factions of Daleks were eventually destroyed, and the Earth was saved from destrucion.

The Dalek-Cyberman War
The first true 'Battle of Earth' involving outside influence from aliens that consumed the entire planet came in the form of two alien invasions occuring at once. The Dalek Cult of Skaro had escaped the Time War and emerged in London in 2006 PLF, declaring war on humanity. At the same time, Cybermen from a Parallel Universe emerged all over the world and the Daleks declared war on them as well. Humanity was essentially caught in the middle of the War between the Daleks and the Cybermen, and after a brief alliance with the Cybermen followed by intervention from The Doctor, the Daleks were defeated, with the Cybermen disappearing shortly after.

Cybertronian Civil War
The next Battle of Earth would take place just one year later, in 2007 PLF, when two opposing factions of the ancient and failing Cybertronian race would battle it out on Earth for possession of several Cybertronian artifacts that had been hidden there centuries before, such as the Allspark, the Solar Harvester, and the Space Pillars. Unlike the Dalek-Cyberman War, the Cybertronian Civil War saw true alien co-operation with Humans, as Optimus Prime of the Autobots sided with Human military forces to destroy the Decepticons.

Human-Sontaran 'War'
It would not be long before Earth was attacked again, as in 2009 PLF, Sontarans attempted to turn Earth into a breeding planet for their clone soldiers by gassing the planet, killing the Humans in the process and terraforming the planet for their own needs. The Doctor intervened once again, this time in an alliance with UNIT, and burned away the gas in the atmosphere and destroyed their primary battleship. Following this, Human forces in the UNSC began to build a Home Fleet for the purposes of defending the planet, starting with the refitting of the Valiant and the attatchment of weapons to the International Space Station.

Reaper War
This fleet would aid Humanity over 100 years later, during the Reaper War which shattered 100 years of peace on Earth and sent the entire Galaxy into disarray. Humanity allied with other races such as the Turians and the Asari, with all races rushing to defend their homeworlds and colonies from the Reapers. The Battle of Earth turned out to be the last battle of the war, with the crew of the SSV Normandy defeating Harbinger and bringing peace to the Galaxy once more - at least for another 300 years.

Human-Covenant War
Earth would come under attack once again, however, in the years between 2525-2552 PLF, when the alien alliance known as the Covenant declared war on Humanity. The Human race put up a good fight, but eventually Covenant forces reached Earth and it was only thanks to the discovery of the Halo Array by Johnny and the splintering of the Covenant under the Arbiter that Earth survived. Following this, Humanity strengthened their defences and began their 1,000 year Empire after surviving attacks from both the Didact, Lord Hood, and Cortana.

Human-Borg War
In 3550 PLF, Humanity was once again challenged by a hostile alien force - this time originating from the Trek Galaxy. The Borg, following a war with the Cybermen, attacked Earth several times via temporal methods but were repelled by Jean-Luc Picard and the crew of the USS Enterprise. Following this, the Borg were all but destroyed and their Queen was killed. Peace would therefore return to Earth for nearly 2000 years.

Second Galactic War
The next Battle of Earth was during the devastating Second Galactic War, a war fought between the League races and the Dalek armada in 5300 PLF. The Human home fleet was annihilated by the Daleks and the Humans were forced to rely on Turian and Sangheili intervention to protect their homeworld. Following a disastrous loss above Earth for the League following a firing of the Reality Bomb, the remaining Human ships launched a desperate attack on the Dalek Crucible which, amazingly, suceeded, forcing the Daleks to retreat.

The Extermination
After 5000 years of peace, the Human race became complacent and its defence fleet became weak, due to a subtle interference by the Dalek Emperor and his flagship, the Exterminator. After 100 years of influencing Humanity, the so-called 'God of all Daleks' attacked Earth with his fleet, causing immense damage to the planet and causing it to be abandoned by Humans entirely, with the species as a whole donating the planet to the National Trust, who began to painstaking 1,000 year operation of moving the continents back into their 'classic' position through geo-gravitational magnets.