The Imperium war machine is built upon a single concept - efficiency. Having the right weaponry for an engagement is often the key to victory and having access to all manner of different ship configurations allows an Admiral access to what she needs, when she needs it. With widespread rail networks extending from Prussia to the other Germanic nations of the Imperium, the navy (known as the Kaiserliche Marine) decided to equip a new generation of warships and support vessels with compatible gauge rails to allow weaponry and goods to be easily changed in short order.
This allows the Imperium to be responsive to the needs of the operation at hand without having to go to the cost or lengthy construction times of creating specific ships to fill those requirements. Should a vessel be needed to bombard an enemy shore battery, then a Blucher cruiser can be modified to create an Augustus Bombardment Cruiser in less than a day. At the Wilhelmshaven Imperial Shipyard, the record stands for the refitting of the warship Stralsund. The cruiser had arrived fresh from hunting corsairs off the coast of Heligoland three hours earlier. In those few hours the yard crew removed her (still steaming) Volt Gun Batteries and installed a Gustav Heavy Bombard in their place.
Unit cards are not included. They can be found on the publisher's website.