Despite the fact the Loyalists were the first faction to actively oppose the Regent, they were not the first faction to form in opposition to his rise to power. That honor goes to none other than Cloudsdale, perhaps the second biggest city in Equestria at the time. Cloudsdale did not support either the seating of a regent or of Blueblood on the throne, neither of whom had served Equestria in any fundamental way before, could do the job properly. They proposed, instead, the creation of a new government, seated primarily by those who served Equestria, be they military or politically inclined. When the Regent was seated, they declared their independence in a way only a pegasus city could — they moved Cloudsdale out into the ocean, outside of Equestria's borders.
When word spread of the rise of the Loyalist faction, they found themselves questioning the situation. Despite their "separation" from Equestria, they were incapable of sustaining themselves without soil to grow food and other resources. Despite breaking away, they still had to abide by trade regulations with the Regent, and he made his disappointment in their response to his rise to power known with brutal trade demands.
Their "alliance" with Equestria was finally tested when pegasus soldiers came demanding the loyalty of Cloudsdale to deal with the growing threat posed by the Loyalists and other factions that began to spring up. If Cloudsdale did not surrender to the Regent's demands, they would sever all trade deals, forcing Cloudsdale to either find new resources or die a slow death. They were about to give in when Spitfire — then the leader of the Wonderbolts, he had become the military arm of Cloudsdale — stepped up and offered another alternative.
"Why not form new alliances?"
In secret, Cloudsdale managed to form an alliance with farms and resources in the Gryphon territories, whom Equestria had begun to shun. Within months, Cloudsdale had the resources to offer an alternative place for the Regent to put his surrender deal.
Cloudsdale was now recognized as its own budding nation, but that was simply the first step of their plan. When Spitfire rose the ranks to become the new Prime Minister of Cloudsdale, she set her sights on a new goal. Equestria needed them, and she would take it back.
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Unlike the other factions, Cloudsdale is in a sense a pre-existing government presence — an entire city with its own political body trying to take control of the larger (but less stable) Equestria. Something of a military state governed by mostly ponies who had served as either Wonderbolts or Royal Guards at one point or another, the city is hidden away from Equestria as while they do not officially declare war, they do lead many covert operations to undermine the Regency. The Cloudsdale Resistance believes that they have the ability to bring order and stability back to Equestria by installing their own pre-existing government in place of the Regency. Lead by a council and a Prime Minister, they desire to turn the leaders of Cloudsdale into the leaders of Equestria as a whole.
Among there numbers are the Wonderbolts, who serve as their military, but also the newly formed Shadowbolts, who serve as Cloudsdale's covert ops, undermining the Regency and attacking his interests, while also keeping an eye on the other factions that sprung up. The Cloudsdale Resistance and the Loyalists are opposed to each other as their goals naturally cannot co-exist; the Loyalists feel that a new government would destroy too much good in Equestria, and Cloudsdale believes Blueblood is a mistake waiting to happen. The McIntosh Alliance views the Resistance as an arrogant and overly militarized force, while they see the Alliance as a backwater group of rejects who have no idea what they're doing. Cloudsdale is the first faction to have also been aware of the presence of Wraith Tower, having noted strange activity in the remains of the Crystal Empire, and a growingainbow surge in magical activity.
The newly formed Shadowbolts — which serve as the black ops arm of Cloudsdale — lead the operations to undermine the Regent and destabilize him as well as any other faction that gets in their way. Key among their leadership are ex-wonderbolts Rainbow Dash and Soarin', as well as their ground operative Scootaloo.
When Equestria began to fall into civil war, Rainbow Dash had already retreated to Cloudsdale, fearing that her circle of friends were growing apart without Twilight to hold them together, though she maintained contact with Fluttershy, who chose to remain behind. In the coming months however, she would learn that the Regency and Loyalists had both sought to capture Discord, believing his alliance could tilt the odds of their success in either of their favor, and that in the altercation, Fluttershy had been killed and Discord had disappeared. Despariing at the loss of yet another beloved friend, and angry that this one was at the hooves of others she had once cared for, Dash was quick to offer her strength to the Shadowbolts.
Scootaloo, whose family had to relocate to Cloudsdale under growing suspicion of her own connections to those related to the ponies now fighting the Regent, also joined the group. Due to a defect that makes her incapable of flight, Scootaloo learned to compensate by learning how to operate a lot of gadgets and vehicles, ranging from hang gliders, to balloons, to zeppelins. Combined with some skills in the building of simple gadgets and explosives, Scootaloo often serves as a combat engineer for the Shadowbolts.
These three friends, among others, tend to have rainbows died in their hair — something that earned them the title "Rainbow Squad."