Military
Ground
Legacy technology is too expensive to exploit on a large scale for weapons, so most soldiers are equipped with ballistic rifles. However, it is quite common for Senior Officers to carry laser pistols as a mark of status. These pistols are not vastly more damaging than standard firearms, but are accurate at longer ranges. Certain specialised forces also equip snipers with laser rifles, though these are not deployed on a large scale due to sheer expense.
Platoons are equipped with heavier weapons such as large and unwieldy autoguns which can fire a bullet every second or so. This is not vastly quicker than experienced soldiers can manage with ordinary rifles, but allows for sustained fire without a loss of aim. Mortars and antivehicular rockets are used to damage vehicles; the prevalance of these countermeasures means that the Empire's cars and buses do not see much use in battle (when they are used, passengers consider them to be death traps). Explosive grenades are also sometimes deployed, though they frequently cause as much damage to the thrower as they do to the enemy.
Cavalry units are relatively common, able to evade rifle fire but sometimes vulnerable to autoguns or heavier artillery. These troops are sometimes armed with pistols and sabres but are also often used as a means of transportation, with riders dismounting and using rifles to fight.
Soldiers wealthy enough to afford a Gravcycle will ride one of these into battle as it makes the rider extremely manoeuvrable and able to evade much incoming fire. Gravcycle troops are normally formed into separate units which are capable of charging down machineguns and decimating infantry firing lines. These troops are often armed with pistols and sabres for close range fighting once the enemy has been engaged. Experiments to incorporate weapons directly into the bikes suggest that this is a difficult problem that will require a skilled Technologist to solve.
Large artillery guns are also used, but are relatively inaccurate due to a lack of extensive mapping and ranging technology. For this reason, they are primarily used by firing them directly at a target rather than using a high firing angle.
Space
Frigates are the most common class of ships used for military operations in space, but this is such a broad category that several subcategories have been devised. Larger classes are designated Battleships or Ships of the Line; these ships are rated according to their firepower. First Rate denotes any ship mounting Legacy laser weapons, whilst Second and Third Rates are differentiated purely by the number of cannon they mount - Second Rates mount at least 80, Third Rates at least 50.
Smaller Frigates are designated Cruisers. These ships mount less than 50 cannon and are able to operate without ammunition resupply for much longer. For this reason, Cruisers have historically been used to strike at enemy military supply lines.
Fighters are used in combination with Spiders to screen ships before they enter the line of battle, to deploy bombs against larger ships and to defend against bombers and boarding chutes.
Boarding chutes are small pods which can be launched from Frigate docking bays at high speed, aimed at other Frigates. The chutes bore holes into the hull of the target ship, sealing the breach with the chute itself. The passengers are then able to disembark and carry the fight directly to the crew of the target ship. Boarding chutes require a Fixed Autofactory to produce, but not many have been found, so these are in short supply. The material cost is also high compared to the military value, so these craft are not often used.
House Armies
Each Noble House maintains an army and a fleet, which are used as part of the Imperial Army, to quell disturbances in House territory and in House Feuds.
Ranks within House armies are:
1. Junior Officer - Lieutenant, Captain, etc. These ranks are held by Officers who command a single ship or army unit.
2. Senior Officer - Colonel, Major etc. These ranks are held by Officers who command a small flotilla or an army task force.
3. General, Field Marshal - These ranks are held by Officers who command a House's entire fleet or entire ground force.
These ranks are normally tied to the Influence you wield within your House's military structure (which is one option you can take within the House Influence skill).
Imperial Army
The Imperial Army is made up from the House Armies, plus commanders from House Lystra and the Imperial Elite Guard.
The Elite Guard is of comparable size to a single House force, but the troops are subjected to the most rigourous training possible. Notably, the Elite Guard lacks a large number of Battleships, preferring to concentrate on ships which will allow it to transport its ground troops easily.
The head of the Imperial Army is known as the Chief of the Imperial General Staff and he is assisted in his command by the Commander-in-Chief of the Elite Guard and the heads of the House Armies.