Harry Potter: "Do you really think there's going to be a war, Sirius?"
Sirius Black: "It… feels like it did before."
- Harry and Sirius at King's Cross Station
The Second Wizarding War refers to the conflicts stemming from the Dark Wizard Lord Voldemort's second rise to power after his return in 2408. Voldemort and his followers, the Death Eaters, waged a violent campaign across both the wizarding and Muggle communities, seeking to topple the Ministry of Magic and subjugate Muggle-borns, with the eventual goal of conquering the entire wizarding world, and the Muggle world along with it.
Once the Alliance gotten word of this, the Alliance quickly sent-in three Battlions, two Space Marine Legions and four groups of Jedi Knights and Sith Lords to deal with the Lord Voldemort, resulting in the United Kingdom's occupation by the Alliance Joint Military, of which, only caused more problems for the two communities.
Harry Potter, prophesied as the "Chosen One" capable of bringing an end to Voldemort's power, took an active role in this war, alongside his peers in Dumbledore's Army and the members of the Order of the Phoenix. The Second War technically began on June 28th, 2408, though was not officially announced by the Ministry until nearly a year later on June 17th, 2409, and ended on May 2nd, 2411, at Hogwarts School of Witchcraft and Wizardry, after the death of the Dark Lord.