"Rolling Thunder" is an attempt to describe the various OGRE units involved in the Last War. From the lowly Mk. I up to the super heavy Mk. VIII and the often misconceived Mk. IX. Falling between the more recognized marks were many interesting variants. The Combine Dark Horse stealth OGRE, the LOGRE, the OGRECOVERY vehicle, the ESPIONOGRE, the OGRECON, the OGRENGINEERING vehicle, the Trojan Horse, the Reaper, the OCP (OGRE command post), Fencer, Huskaral, and the first Sentient Forts (immobile OGREs, both land and sea variants) all played key roles in the Last War.

The various Marks of OGREs are all well documented in the Historical Archives of the Last War. Audio and visual files (still and all aspect sensory motion) exist of all the popular models. However, there were many variants of the basic models, used for special missions and operations. These are not as well known, due to their low production numbers, but they are nonetheless worthy of mention.

The Combine's experiments with battlefield mobile artificial intelligence were far more successful than those of the Paneuropeans. In fact, the Paneuropeans were only able to produce and field successful OGRE units after they had captured the Sheffield Complex. However, much of the plans were ruined by the retreating engineers, and the Paneuropean technicians never fully grasped the details of the Combine AI models. As such, the Paneuropean cybertanks were less technologically advanced than the Combine models, and took longer to field successfully.  The logistics and maintenance service required to keep the Paneuropean cybertanks in operation were also far greater than the Combine counterparts.

The cybertank was a virtual Pandora's Box on the battlefield as its deployment had opened up many new (and frightening) aspects of systematic / automated warfare. The experiments continued throughout the Last War, each new breakthrough being rushed into service as more breakthroughs were looming on the horizon. Operating Systems advanced quickly, leading to greater armament, higher accuracy, and higher probability of survival and mission success.

The cybertank was not only used as a assault unit, several different models appeared to fill the mission assignment tables for the Combine doctrines. The Combine was notorious for producing new models and designs, pushing the utility and effectiveness of the cybertank to newer and higher theoretical limits all the while keeping with a design philosophy of maintaining the most parts interchange possible between models. The core command center from a wrecked chassis could be removed and placed into a lower or greater chassis.  Such was the Combine design philosophy. On the modern battlefield, modular design and wide spread interchange is key to success. The Combine realized this early on, the Paneuropeans learned it the hard way; from the Combine and from actual combat field experience.

The Paneuropean artificial intelligence and computer controlled vehicle programs were not quite as advanced as the Combine programs, and as such, each new type of Paneuropean cybertank shared very little in the way of component parts with any of its predecessors. This led to a greater amount of frustration among Paneuropean field technicians than was shared by their Combine counterparts. It also meant that field stripped Paneuropean cybertank parts could only be installed on similar models. Not good if you needed parts for a Mark V and all you had was two smashed Mark IIIs. Many a Paneuropean Field Tech, especially those stationed in the Sahara Combat Zone, questioned on many, many occasions the design philosophy of their superiors when it came to fielding such massive engines of destruction, and they looked upon their Combine counterparts with a certain professional jealousy.

By and large, Combine cybertanks were in and out of depot maintenance far quicker than their Paneuropean counterparts, and they spent less time in the depots for routine maintenance, reloading, and servicing. A fact that ultimately helped the Combine achieve its major victories over the Paneuropean forces in the early to middle stages of hostilities.