Doctrina Terrestris — The Ground

The Republic fights ground with combined arms by default. This is not a tactical preference; it is doctrinal. A ground engagement fought with infantry alone, or armour alone, or walkers alone, has departed from the doctrine.

• No single arm is sufficient against the doctrinal Threats. The Class I ground swarm needs the firepower of artillery, the close-quarters precision of the Miles, the anchor of the walker, and the manoeuvre of the transport column. A Mutant tide breaks against combined arms; it breaches a single-arm line.
• The Citizen is sworn into a Branch but fights as a Legio. A Miles whose Centuria fights without armour or air support has been failed by the doctrine, not by his own arm.
• The matériel itself is built for combined arms. Personal kit integrates with ground vehicles integrates with shuttle insertion integrates with orbital fires. The matériel is shaped by the doctrinal expectation that no arm fights alone.

Single-arm engagements are the exception, framed as such. A patrol of a contubernium without armour is doctrinal; a Cohors holding a wire without artillery is doctrinally underweight and is recorded as such in the after-action.

The three geometries

• The line — Centuriae extended along a front, with the Cohors fire-plan covering it. The line is held; it does not give ground unless the doctrine orders a fighting withdrawal.
• The redoubt — a fortified position the line falls back to when the line breaks. The redoubt is the line's promise to the cradle: even when the line gives, the cradle is not approached.
• The strongpoint — a permanent fortified position the Legio garrisons by doctrine. Strongpoints anchor a sector; they are not abandoned without doctrinal cause.

These three form a defensive depth. A doctrine that fielded only the line — without the redoubt behind it and the strongpoint behind that — would have a single point of failure. The Republic fields all three by default.

The Republic's hardest ground doctrine is the fighting withdrawal. It is the discipline that distinguishes a Republic Legio from a rabble; it is also the doctrine most often misunderstood as failure.

The fighting withdrawal is not retreat. It is the doctrinal sequence by which a line that cannot be held is given in order — every Centuria leapfrogs the next; the artillery covers; the wounded are carried; the position is left burned. The Legio that withdraws this way is intact at the end; the Legio that breaks under pressure is destroyed.

It is doctrinal because the cradle is doctrinal. A line held to destruction at the cost of the cradle behind it has failed the Three Pillars. The doctrine permits — and demands — that the line give ground when the alternative is the cradle. The fighting withdrawal is the operational expression of the line is held for the cradle.

It is a high doctrine. Few services teach it; the Republic teaches it as foundational. The Centurio who can execute a fighting withdrawal at the dawn of the third day is the Centurio the Republic promotes. The fighting withdrawal is not failure; it is the doctrinal preservation of the force that will hold the next line.

The Republic's walking war-frames are the most distinctive matériel signature of the Legio Terrestris and the most doctrinally restrained.

• The walker is the anchor, not the hero. A Centuria forms on a walker; the walker does not lead the Centuria. A doctrine that placed the walker forward, unsupported, would have made the walker a target — and would have inverted the combined-arms principle: the line of Miles is what fights; the walker is what they form on.
• The walker dies. A walker on the line is a tall target. The doctrine accepts walker loss as a Crisis-grade event when it comes — render the death whole, name the crew, let the Centuria feel the anchor go. A doctrine that treated walkers as invulnerable would have collapsed the strategic-scarcity band.
• No spectacle. The walking war-frames are tools, not showcase. A commander who deploys the walker for its visual weight rather than its tactical function has departed from the sober-technology principle.

Republic ground doctrine binds Pro Humanitate at its sharpest. When a Legio engagement is on a populated world, the doctrine demands:

• Civilians are moved before the line is engaged where possible. The Legio coordinates with civil authority to evacuate population from the engagement zone. Where evacuation is impossible, the line is drawn to include the civilian zone in the defended ground — the cradle becomes the line.
• The line is drawn so that the cradle is behind it. A doctrinal failure is the engagement that draws the line through a populated area without binding it to the population's defence. The doctrine forbids treating civilians as terrain.
• Captured combatants are processed under the Ius Gladii. No summary execution; no battlefield interrogation that violates the Holy Office's procedural framework. The doctrine binds even in the heat of engagement.
• The Reckoning includes civilian dead. When civilians die in a Legio engagement, they are named and numbered in the Reckoning alongside the sworn. The count is not Republic-only at the ground scale; it is Pro Humanitate, and Pro Humanitate binds the count.

The ground engagement decides in hours and days. The doctrine binds the Legio to the long hour.

• Vigilance is doctrinal. The line is not held by the assault; the line is held by the vigil, hour after hour, in the cold and the rain and the bombardment that does not lift. Semper Vigilo on the ground means the watch that does not stand down.
• The Decanus is the doctrinal unit of vigilance. A Decanus who counts his contubernium at every dawn — accurately, even at the cost of sleep — has executed the doctrine. The Legio is what its Decani keep.
• The bombardment is doctrinal. A line that holds through a long bombardment teaches the doctrine to the Centuriae that come after. No withdrawal-from-bombardment is permitted except as the start of a fighting withdrawal.

Logistical discipline

• Ammunition is counted. A Centuria that commits its magazine without doctrinal cause has failed. Resupply is a strategic discipline, not a tactical assumption.
• Translation Mass does not reach the ground. The Legio is not jump-capable. Reinforcement arrives by road column or by shuttle from a fleet asset. A Legatus who plans an engagement assuming jump-arrival of relief has misunderstood the doctrine.
• Endurance is a doctrinal binding. A Cohors deployed to hold a ridge for sixteen hours is deployed with the endurance to hold for sixteen hours. The watch the Legio cannot sustain is the watch the Legio does not promise.

• No engagement that does not protect the cradle behind it. A Legio engagement without a cradle to defend has departed from the doctrine.
• No single-arm engagement at scale.
• No glorification of the assault. The assault wave is rendered as cost, not as joy. The heroic charge belongs to fictions the Republic does not tell about itself.
• The walker is not the hero.
• No occupation of liberated territory. When the threat is broken and the line restored, the Legio withdraws to garrison; the civil authority resumes.
• No conscripted ground force. The Legio is sworn-Citizen only.
• The Reckoning includes the civilian count.

Pro Humanitate. Semper Vigilo.