Decepticon Civil War

The Decepticon Civil War is not a single conflict but something that has repeatedly happened whenever there have been leadership disputes among the Decepticon army. It differs from the usual punch-up between disputing leaders in that the Decepticon Civil Wars involve conflicting groups of Decepticon soldiers.

Sometimes they're really quick, sometimes they last for a long time, and neither time do the clashing leaders solve things with a coin toss.

Ratbat/Scorponok
A brief conflict, this was organised by Starscream to allow him a shot at the Underbase. The Earth-based Decepticon platoons under Ratbat and Scorponok had been acting completely independent of each other, with seemingly little interest in working together on Ratbat's part (Scorponok's entreaties had been covered up by Starscream). With the situation already tense, an "accidental" revelation of the Underbase sparked off a brief and violent conflict. It reaffirmed that Buzzsaw is slagging nasty.

Scorponok/Shockwave
While believed dead, Shockwave began plotting against the current Earth commander Scorponok, believing him unsuitable for the role. While Shockwave did recruit some of Scorponok's men to the fold, the bulk of his troops were Decepticons believed to also be dead, allowing for nobody to see him coming. In their first strike Shockwave's group obliterated Scorponok's Jersey base before he personally engaged Scorponok

The intervention of the Autobots and Neo-Knights caused Shockwave to be taken out and the war end in Scorponok's favour.

Scorponok/Megatron/Shockwave
In a divergent timeline, 1991 saw a three-way version of the above civil war, with Megatron involved. The involvement of Megatron caused this war to end badly for Scorponok - he was left defeated, wounded and pursued by Megatron's Air Strike Patrol. Only by surrendering to the Autobots and thus forcing them to protect him (while he walked off) did Scorponok even survive. As Shockwave was later seen under the control of Megatron (and chafing under it), we can safely assume Megatron was the victor.

Megatron/Shockwave
Both revived along with some of the Underbase-offlined soldiers, Megatron and Shockwave began fighting a Decepticon Civil War on Earth for command of the whole army. The Autobot Earthforce was created to contain them.

The Decepticons would spend as much time fighting each other as targeting Autobots. Realising this was giving the Autobots the strategic advantage, they called an Enclave to settle their differences but the Autobots sabotaged it.

This civil war ended when Starscream & Soundwave betrayed Shockwave & Megatron, took command of the two factions, and then united them under a dual leadership.