Operation Revolving Door

The Operation Revolving Door or Operation Rot-Gelb is a series of military operations executed by the Imperial Army during the Great War. Its goal is to destroy the whole Republican Rhine Army Group by luring them into the trap and encircling them. At last, except of Armored Division 3, Strategic Mobile Army 7, and some infantry units guarding the capital, the majority of Republican Army were destroyed in the Low Lands.

Background
As the Empire gradually pushed the front line, they finally retook the Low Lands Industrial Region and marched into the Republic border. At that time, a massive trench warfare was ongoing on Western Front. Both belligerents were searching for the way to break the stalemate.

The Empire
At the joint meeting of the Service Corps and Operations in April 28, 1925, several Imperial staff officers were discussing about the pros and cons of the Rhine offensive plan. At that time, the Entente Alliance was essentially collapsing, yet it still held up the Imperial Army in north. In short, Northern Army Group was not in situation where it could spare troops to reinforce the main fighting lines on the Rhine until next spring.

Meanwhile, the navy was in the process of gaining superiority in the channel against the Republic. The navy apparently couldn't wait to break through the channel, which met their ambition to wipe out the Republic fleet in a battle of warships. However, both von Zettour and von Rudersdorf, the deputy director of the Service Corps and the deputy director of Operations, agreed that once they enter the channel, the United Kingdom, a neutral great power, will probably interfere to maintain the balance of power, which means their current superior position might reverse.

Above all, the General Staff realized that achieving victory by attacking the enemy castle and forcing them to sign a capitulation was no longer possible in the war between two great powers. They also found it fundamentally impossible to ally break through the enemy trench in Western Front. It's time to make a paradigm shift, and for this reason, General von Zettour proposed:
 * “The goal of the operation shouldn't be to break through. It should be to bleed the enemy. To put it in another way, our offensive plan should be to wear out as many enemy soldiers as possible.”

In brief, he suggest leave parts of their territory undefended and prioritize wiping out the enemy field army. Finally, the General Staff reached a consensus to modify the offensive's aims to annihilate the enemy's field army instead of push the front line.

Preparation
Rudersdorf, the deputy director of Operations, drew up a decisive battle plan to lure the Republican Army in and destroy them. In his original plan, the right wing of Imperial Western Army Group will retreat from Low Lands Industrial Region, enticing the Republican Army to march into it. Next, they will send a special ops mage company to attack the enemy headquarter directly to cause disorganization of the enemy. Once the operation succeeds, the Imperial left wing in Mesienn Highlands will explode a series of underground explosive charges, secretly planted beneath the trenches of Republican Army here. Later, the armored units and mechanized infantry concentrating at the left wing will break through the enemy front line and try to encircle the Republican Army in Low Lands.

To send the mage company to the enemy headquarter, the General Staff adopted a new weapon named “V-1” or “additional acceleration apparatus”, which was originally a failed product of new aircraft invented by Chief Engineer von Schugel for reconnaissance-in-force. It is a powerful aircraft that could penetrate the enemy's interception lines by its extremely high velocity and flight altitude, but it can only land by crashing the ground. An officer from an airborne unit found its value in airborne warfare. Think differently, if let the pilots eject from it, it would be a more reliable way of delivering mages behind enemy lines than paradropping. At that point, the project was prioritized by the guerrilla warfare proponents, and it received literal leverage from the General Staff. Eventually, a first run of 20 mass production models was rolled out in a hurry, and the General Staff made a slight but significant amendment to their offensive plan, which later became the additional phase “Operation Shock and Awe”.

Coincidentally, the uprising of Arene occurred, which also gave the General Staff an opportunity to execute their deceptive operation.

Phase One - Operation Fog and Sun
The General Staff concluded that it wouldn't be possible to hide the activation of the rail network that would accompany the large-scale maneuver in the theater, so instead they deliberately spread false information about the gathering of supplies and troops before a major offensive. In Berlun, a public relations officer made reference to a “large-scale operation,” albeit in unofficial settings. They also thoroughly censored the reports on Arene to mislead the informed people that the movement on the Imperial side is reinforcements for the suppression of the revolt in Arene.

May 10, 1925, the Imperial Army frequently performed recon-in-force to hold up the Republican Army as the majority secretly retreating. By burning several Republic supply depots, they shifted the attention of Republican Army Command onto the invading forces and the upcoming major offensive. Moreover, apart from the delaying at the beginning of the war, the Empire had always defended its territory to the end. Eventually, the right wing of Imperial Western Army successfully retreated from Low Lands without the Republican Army noticing. They abandoned most heavy artillery guns, thoroughly demolished the proper Low Lands sea access point, set the underwater mines in the ports, and concentrated several armored units and mechanized infantry in the left wing in Mesienn Highlands.

May 18, 1925, the Republican Army emerged from its heavily fortified lines and was launching an advance into the wide-open vacuum the Imperial Army had left. By now, the Empire had lost the Low Lands Industrial Region which they retook by sacrificing countless lives of their soldiers, and even the Western Industrial Region, the main Industrial Region of the Empire, had been within the range of the Republic heavy artillery guns. In Zettour's words, they had crossed the Rubicon.

Phase Two - Operation Shock and Awe (German: Unternehmen Schrecken und Ehrfurcht)
May 25, 1925, a special ops mage company detached from the 203rd Aerial Mage Battalion had prepared to attack the enemy Forward Headquarters Complex. Based on the information from the Imperial intelligence, they got 3 positions that might be the location of the Republican Rhine Army Group Forward Headquarters. After the landing of the V-1, they found V-1 failing to hit their targets fully, and since the Republican was attacked by the missile for the first time, they didn't expect there would be the airborne mages ejecting from the missiles. The company formatted into 3 platoons and attacked 3 positions respectively. Within 10 minutes, they destroyed all three targets (position A is an unknown intelligence facility, position B is the Republican Rhine Army Group Headquarters, and position C is the wrong target, though it was a potential munitions reserve warehouse) and escaped to the north where the submarine was awaiting.

Phase Three - Operation Lock Pick
As receiving the success code from the mage company, the Imperial Army executed the next operation at once. The left wing of Imperial Army in Mesienn Highlands detonated a series of underground explosive charges beneath the trenches o thef Republican Army here. Next, the vanguard troops combined with armored units, mechanized infantry, aircraft, and aerial mages started breaking through the Republic front line. At that time, the Republican 10th Division bore the shock from the Imperial vanguard troops first, yet the warning never reached their reserve troops to counterattack due to the destruction of their Forward Command and Communication Complex buildings. On the same day, the Empire received the request from the Commonwealth to “restitutio in integrum”, and was rejected. The Imperial vanguard troops kept marching and isolating the disorganized enemy. May 27, 1925, the encirclement was a success.

Phase Four - Attack Plan 177
As the main forces of the Republican Army were disorganized and encircled in the Low Lands, the Imperial Army started reducing the pocket of resistance. The Imperial Navy had built the blockade line in the coastal area of the Low Lands, and the Imperial Army also built the aerial warning net to avoid the partial inferiority usually occurred in total encirclement. Although a Commonwealth mage battalion invaded the aerial warning net, they were repulsed by the Imperial aerial mages. Eventually, all Republican Army in the pocket had surrendered.

Aftermath
Since most of the Republic Army had been wiped out, the collapse of the Republican Rhine Army Group was undeniable. It gave the Empire an opportunity to end the bloody trench warfare and take back the peace.

Reference
Plus Ultra - Chapter V The Devil of the Rhine Plus Ultra - Chapter VII Preparation for move forwards The finest hour - Chapter I Open Sesame The finest hour - Chapter II The Intervene, which was too late Anime Episode 9 Anime Episode 10