Igor Kolomoisky, a prominent Ukrainian businessman and founder of the country's largest commercial bank Privat Bank, took office in Dnipropetrovsk in March 2014.
Dnipropetrovsk became the front line in the battle between pro-Russian separatists in the east and Ukraine government forces.
He quickly set about recruiting and training volunteer "self-defence" forces that would become the Dnipro Battalion as well as a number of smaller groups that manned checkpoints.
The battalion was equipped with new SUVs, armoured cars, machine guns and grenade launchers, body armour and new uniforms at a reported cost of $10 million.
It was widely seen as being better equipped than Ukraine government forces and National Guard units.
In total the Dnipro Battalion was reported to number 2,000 combat ready troops with a further 20,000 reserves. In other words, it became a sizable private army.
And they proved an effective force on the battlefield. In August-September 2014 the battalion took part in fighting in the rebel-held Donetsk region, but were routed by pro-Russian forces in the battle for Ilovaysk.
Following the second Minsk ceasefire agreement reached between the two sides in February, the battalion has mostly been patrolling the border between Dnipropetrovsk and the breakaway regions.
That is, until last week when armed men in masks stormed the offices of UkrTransNafta in Kiev following the sacking of its chairman, a key ally of Kolomoisky.
The ensuing stand-off saw Kolomoisky emerge from the building to clash with journalists while his supporters decried the government's actions.
In response, President Petro Poroshenko told troops in the Ukraine capital that no regional governor would be allowed to have a "pocket army" in a move that looked likely to set him on a direct collision course with his former ally.
And on Tuesday evening, news came through that Poroshenko fired Kolomoisky from his position as governor of Dnipropetrovsk.
The question that everyone is asking now is what will happen to the battalions funded by Kolomoisky? Can the state disband a "pocket army"?
