Operation: Volcano refers to an aborted uprising by the Autobots of Cybertron against the Decepticons of that world.
Background[]
In the Marvel UK continuity of comics, by the year 1986 Cybertron had been completely conquered by the Decepticons, the remnants of the Autobot army reduced to fighting a guerrilla war for thousands of years after the destruction of Iacon, the last of their refuges. The leader of the Autobots throughout this period was Emirate Xaaron, last surviving member of the Autobot Council of Elders, and the very being who had placed Optimus Prime in command of the war effort.
The Plan[]
Operation: Volcano was the result of many years' planning and coordination between the various Autobot resistance cells and underground leaders across Cybertron. In essence the plan was simple -- the Decepticons' ten deadliest warriors were to be lured by the possibility of capturing or killing Emirate Xaaron and would be ambushed by the Autobots' elite warrior squad, the Wreckers led by Impactor, and possibly the Autobots' best warrior on Cybertron at that time, Ultra Magnus. The elimination of these Decepticons was to coincide with a general Autobot uprising across Cybertron, hopefully leading to the Autobots regaining the initiative in the war against the Decepticons.
The Implementation[]
Unfortunately, things did not go as planned.
"Another fine mess you've gotten us into, Laurel..."
The Matrix Flame, which indicated the continuing survival of the current bearer of the Matrix of Leadership went out suddenly and inexplicably shortly before the operation was due to commence. (Although the actual explanation was because Optimus Prime had been displaced into limbo thanks to the arrival from 2006 by the Decepticon Galvatron). As such, Ultra Magnus was dispatched to Earth to try and discover the reasons behind Prime's disappearance, with only a finite time available to do so. In doing so he missed the deadline to return to Cybertron before the operation began.
Emirate Xaaron did draw out the Decepticons by addressing a "meeting" of Autobot leaders (which were in fact nothing but facsimile constructs). Kickback reported back to Decepticon High Command as to Xaaron's presence, and Decepticons including Dirge, Ramjet, Thrust, the Insecticons, and a new member of the team by the name of Macabre were dispatched to the location. The Wreckers were aware of Kickback's presence and were preparing to lay the ambush for the Decepticons.
However, just before the Decepticons fell into the trap, Megatron established communications with Cybertron and demanded the presence of the Coneheads and the Insecticons with all possible speed over the Space Bridge. As such the Decepticons -- all but one -- broke off their march and returned to headquarters. Fearing the security of the operation had been breached, Xaaron ordered Operation: Volcano be cancelled, and the uprising was postponed indefinitely.
Unfortunately, the one Decepticon who had not followed orders, Macabre, had penetrated the meeting and attempted to assassinate Xaaron. Impactor threw Xaaron out of the way of the killing shot and instead was killed. Macabre lined up for a second shot but was brought down by fire from the rest of the Wreckers. Impactor passed leadership of the Wreckers to Springer before dying. Target: 2006