The Stellar Guard naval forces have highly flexible formations, so no two of
the following units will have exactly the same strength. Still, the basic units
are relatively consistent in mission, if not in exact size.
This is the only organization that is fixed officially. Fleets are assigned to sectors of space, and are rarely seen together. If an entire Fleet is in orbit over a planet, then the Stellar Imperium wants the planet very badly and expects a major naval fight to get it.
Occasionally, two or more Fleets are organized together in one region. This is very rare, since no naval force to date has the strength and technology to stand up to even one fleet. However, when it happens, another admiral is appointed Fleet Admiral to command the combined forces.
A fleet, on paper, consists of three main elements: the battle line, the
carrier force, and the assault force. The battle line consists of four to six
battleships and battlecruisers with their supporting ships. This is the force
that conducts space to surface bombardment, and shows up to deal with major
enemy naval forces. The carrier force assigned to a fleet is also usually four
to six task forces strong. These carriers can both patrol systems independently,
and cooperate with battle and assault units to provide fighter cover for either
fleet combat or assault operations. The assault force contains enough assault
ships to transport at least a corps. In sectors where combat is common, or where
there are unexplored systems, the assault force usually has enough capacity to
transport an army or army group.
This is the most common organization to see. These are, officially, ad hoc collections of cruisers and smaller ships around a capital ship or assault squadron. In reality, most task forces stick together for quite some time, since the rear and vice admirals that command them enjoy knowing what they're dealing with.
A typical task force has two or three cruisers and four to six destroyers
and/or frigates surrounding the main ship(s). Usually, a given mission will
require more than one task force. In such cases, the order of precedence goes:
battle task force commander, carrier task force commander, assault task force
commander for space operations, and the assualt force commander is in charge of
all space to ground operations.
These organizations are really ad hoc. In most cases, a task group consists
of either one cruiser and two to three destroyers and frigates, or four to six
destroyers and frigates. Task groups usually are for patrol missions, checking
in on systems and hunting pirates. Typically, a task group is formed from
whatever collection of ships is available at a given fleet base at a time. Also,
task groups can be formed when ships that have been operating independently need
to group up to carry out a mission. Rarely will a task group include capital
ships or assault ships: the big boys are too valuable to risk outside of a task
force.