Doctrina Conjuncta — Unified Command

The doctrinal authority of a combined-arms engagement is the Legatus Operationis — the operational commander designated to coordinate the Branches for the duration. This role is doctrinally distinct from any Branch's standing command.

• Appointed for the operation, not for the standing service. The Legatus Operationis is appointed at the start of the operation and dissolves back into the Branch command at its close. The role is not a standing rank; it is a commission for the engagement — because combined arms is a doctrinal exception, not a standing posture.
• Drawn from the senior Branch officers present. Whichever senior officer the operation's character makes most appropriate. The choice is doctrinal, not formulaic — a defended-world engagement may make the ground commander the natural unified hand (the line is on the ground); a system-mouth engagement may make the fleet commander the natural choice.
• Sworn to the engagement, not to a Branch. Once appointed, the unified commander's first loyalty is to the engagement's success, not to the Branch she came from. A Legatus Operationis who favours her home Branch in the allocation of resources has failed the doctrine.

What the unified command does

• Sets the operational tempo — when the engagement opens, pauses, and closes.
• Assigns layered objectives — what each Branch's formation is committed to.
• Allocates reinforcement — which layer receives the reserve when a layer breaks.
• Coordinates fires across layers — orbital strike answering ground request, naval gunfire supporting a landing, wing strike crossing all three.
• Holds the operational channel — the single channel every Branch's senior officer hears at the same moment.
• Closes the operation — declares the engagement over and returns the Branches to their standing chains.

What it does not do

• It does not command individual hulls or units directly. Each Branch retains its operational chain. A Legatus Operationis who micro-manages a Centuria on the ground or a frigate's gun-deck has departed from the role's doctrine.
• It does not override the Branch doctrines. It coordinates between layers and cannot direct a Branch to act against its own doctrine.
• It does not commit the Imperial Armada.
• It does not exceed the operational scope. The unified command is bounded by the engagement — not a licence to expand the operation past the threat that called for it.

The combined-arms doctrine's central honesty is the mixed clock: the void engagement decides in minutes, the wet-water engagement in hours, the ground engagement in days, the air threading all of them at the carrier's cadence. The doctrine accepts this asymmetry as binding.

• Layers run at their own tempo. The doctrine forbids the unified commander to attempt clock-synchronisation across layers. A commander in orbit cannot be ordered to delay an engagement to match the ground line's slower tempo; a commander on the ground cannot be ordered to accelerate a withdrawal to match the orbital line's closure. Each layer runs at its own clock; the doctrine codifies this as a feature, not a problem.
• The unified command thinks in mixed time. The Legatus Operationis must hold a picture in which an orbital Reckoning is being read while the wet-water Crisis is at its dusk and the ground Deployment is still digging in. This is doctrinally demanding; the Republic's combined-arms training is built around it.
• The asymmetry shapes the operational channel. Reports arrive at the layers' tempo, not at a uniform interval. The channel is not a synchronous instrument; it is a layered one, and the doctrine binds the unified command to read it as layered.

Where each Branch doctrine names the cradle within its layer, the combined-arms doctrine names the cradle as the single doctrinal anchor across all layers. The orbital line shields the cradle from extra-system threat; the air corridor shields it from atmospheric assault; the coast shields it from the sea; the ground line shields it from the surface. Four shields, one heart.

• The cradle has priority across layers. When the unified commander must choose which layer to reinforce, the doctrinal criterion is which layer's collapse most threatens the cradle. A doctrine that prioritised tactical advantage over cradle-defence has departed from the Three Pillars.
• The cradle's count is the operation's count. The Reckoning names the dead across every layer — orbital crew, wet-water complements, ground Centuriae, wing pilots — and the civilian count from the cradle the engagement defended. The unified Reckoning is doctrinally larger than any single Branch's; it carries the whole world's count.
• The cradle survives the operation by doctrine. An engagement that won every layer but lost the cradle has failed the doctrine, even if the after-action would read as victory. The cradle is the doctrinal measure; the layers are means.

The doctrine names a specific tragic register: the broken theatre. One layer has failed — the orbital line is gone, or the coast is taken, or the inland is overrun, or the wing is destroyed — and the remaining layers must hold without it.

• The broken theatre is anticipated by doctrine. Republic training assumes one layer may fail in any given engagement. The doctrine does not pretend all four layers will always hold; it builds the operation so the remaining three can carry it when one breaks.
• The hardest decision is which layer to let break further. The criterion is cradle-priority — but the choice is rarely clean. The doctrine accepts that the unified commander may make the wrong call; the wrong call is paid for in dead Republic; the Reckoning holds the cost; the doctrine does not punish the choice itself, only the abandonment of doctrinal criteria.
• The terminal broken theatre is the cradle defence. When every layer has bent or broken and the line has fallen back to the cradle itself, every Centuria, every hull, every wing, every Citizen is committed to the cradle's perimeter, and the count that follows is the operation's terminal Reckoning.

The cascade Turn

Unlike the single-layer Turn, the cascade is a sequence — one layer's success re-stabilising another that re-stabilises a third: the orbital line cleared; the carrier freed to launch a strike inland; the strike supporting the ground line, freeing the reserve; the reserve moving to the coast, freeing the wet-navy to close the strait; the convoy through; the world held.

The cascade is the widest heroic register the doctrine permits — every Branch in the same beat, every layer in the same Reckoning, the world held by layered defence operating as designed. It is rare; most engagements decide at a single layer's Turn. But the doctrine teaches the cascade as the ideal, because it is the doctrine's own argument: no layer alone, every layer together.

At combined-arms scale the Servitor Vox becomes a doctrinally distinct instrument: the single voice that can speak across every layer at once.

• The operational channel carries the Vox. It is held by the Vox, voiced by the Vox, and used sparingly by human commanders. Routine traffic is the Vox's voice; a human commander breaks onto the operational channel only when the operation must hear something now.
• The Vox speaks the cross-domain count. Names of hulls from orbit, names of ships sunk at sea, names of Centuriae spent on the ridge, names of wing pilots not returned — all in one Reckoning, all in the Vox's voice. The doctrinal closure of combined arms is the Vox naming the world's count.
• The Vox does not command. The Legatus Operationis commands; the Vox serves the command's voice. A doctrine that ceded tactical authority to the Vox at this scale would have collapsed the human-integrity principle.

The Imperial Armada in combined arms

• The Armada is the last reserve. A combined-arms operation does not plan around it. The unified commander commits the regular service; only if every reserve has been spent and the cradle is at extremity does the doctrine permit a request that the Emperor commit it.
• Its arrival is the heroic register at maximum amplitude — once in a long arc, paid for in the world's near-fall.
• The Emperor remains off-page. Even when the Armada is committed, the Emperor is not named, not depicted, not voiced. The Armada speaks for him.

Pro Humanitate. Semper Vigilo.