Running from 2813 to 2814, the Taurian-Canopian War (also known as the Magistracy-Concordat Conflict, the Herotitus Crisis, the 200 Hour War, the Nineteen-Days War and even the Shoving-Match War) was a border dispute between the Taurian Concordat and the Magistracy of Canopus over the possession of four worlds along their shared border; Detroit, Herotitus, Portland and Spencer.     
Among the initial seeds of the conflict stretched back to the Star League era and the disputed ownership of the "free worlds" of Detroit, Herotitus and Spencer. Located near the rimward fringes of the Capellan Confederation, all three worlds were settled in the wake of the Reunification War by a mix of Canopian and Taurian colonists and both realms believed they had the better claim to control all three. Unfortunately in one of the many examples of the Star League's indifference to Periphery affairs, the League ignored any attempted settlement by both parties and imposed a treaty that arbitrarily awarded nominal control over Detroit and Herotitus to the Magistracy and Spencer to the Concordat. Additionally, each Territorial State's control over their respective worlds was also heavily restricted, similar to the Jointly Held Worlds policy in the Inner Sphere the treaty forbade the posting any military force stronger paramilitary militia on any of the worlds, with Star League peacekeepers maintaining watch posts on each world. In truth the Star League "observers" largely took note of any valuable resources found or industries created that that could be exploited by the Inner Sphere. Following the collapse of the Star League, both the Magistracy and Concordat quietly "upgraded" the garrisons on each world.  
In the later decades of the apocalyptic First Succession War, despite the fact the Federated Suns had it's hands full against the Capellan Confederation and Draconis Combine, many Taurians and specifically then-Protector of the Realm Semyon Calderon's paranoia about a imminent Davion invasion of the Concordat had reached fever pitch, steadfast even in the face of all evidence against that the desperate and depleted House Davion would seek to recoup its loses by striking the Concordat. Convincing his Privy Council of the need to expand the Taurian's resource base ahead of any potential FedSuns invasion, Semyon selected Detroit and Herotitus as a means of achieving this goal, as well of reclaiming "rightfully" Taurian worlds denied by Star League oppression. While self-sufficient and resource-rich, both worlds were a considerable distance from the then-present borders of the Concordat, additionally both were much closer to the Capellan Confederation than any Federated Suns world, raising questions to their value in assisting in preventing a Davion invasion.  
The Taurian offensive began with Taurian Defense Force commander in chief Marshal Gertrude Blake-Andrews assigned to the two-world invasion's strategic command, seconded by Comptroller Augustin Shapiro. 
The Taurian invasion of Herotitus would be doomed from the very start thanks to the arrogance of its commander, Augustin Shapiro. With advance scouts indicating the Canopian garrison on Herotitus lacked much in the way of BattleMechs, the Second Pleiades Hussars did not even attempt to conceal their arrival at the planet's zenith Jump Point and secured the local recharge station without even trying to interdict its communications. Comptroller Shaprio's decision was one of psychological warefare, in clearly announcing the superior might of his 'Mech regiment and its supporting armor and infantry, he hoped to demoralize the MAF troops into surrendering and avoid a protracted fight.  
In truth the intelligence reports Shapiro had received were flawed, while the MAF garrison indeed had a relatively small 'Mechs element, the Taurian scouts had failed to uncover that this lack was compensated by a significant volume of aerospace assets. Thus with eight days to prepare, a large mix of Canopian Aerospace Fighters, Small Craft and low flying DropShips swarmed the shocked Taurians as they entered planet's atmosphere, inflicting heavy losses including Comptroller Shapiro, whose command ship proudly entered the atmosphere first - and thus was the first to die in the maelstrom. Ultimately barely more than two companies of Concordat BattleMechs and half a mixed regiment of infantry and armor made landfall, with Subaltern Josiah Brandamas of the 19th New Vandenberg 'Mech Company the highest ranking officer left. Recognizing the utter hopelessness of his situation, Brandamas chose to save the surviving Taurian troops by signalling his surrender before he even opened his DropShip's hatches, a decision that would earn him decorations after he and his troops eventually returned to Taurian space.  
The Taurians fared somewhat better on the low population world of Detroit, lacking a recharge station to provide any early warnings, Marshal Blake-Andrews took great pains to avoid announcing her presence to the Canopian garrison, nor did she skimp on her aerospace escort. As a result the bulk of her invasion force - the Red Chasseurs 'Mech regiment, plus two regiments each of armor and infantry - were able to reach the surface alive. Once on the ground though, the Taurians and Canopians mostly chased each other around the few military significant targets trying to draw the other side out into ambushes. With neither commander foolish enough to oblige the other by running into the prepared meat grinders, 'fighting' on Detroit faded into a series of defensive holding actions and probing raids until word of the truce arrived.  
Upon receiving word of the Taurian assault on Herotitus, an incensed Magestrix Rwannah Centrella ordered the Magistracy Armed Forces to retaliate in kind, choosing as their first targets Spencer and Portland. While Spencer was a disputed free world like Herotitus and Detroid, the selection of Portland, an actual Concordat system, was intended by the Magestrix as a warning that the Magistracy would not be easy prey.
In many respects Spencer was the MAF's turn to play the patsy; practically Herotitus in reverse. Magistracy DropShips carrying Kossandra's Volunteers BattleMech regiment, a mixed armor and infantry regiment and two squadrons of aerospace fighters arrived via the system's zenith jump point and burned straight toward the planet and its capital of Liberty Point. Upon learning of the Canopians intended target, Comptroller Hendras Mohandun ordered the complete evacuation of the capital before hiding the majority of his militia force, a mixed regiment of 'Mechs and armor, within the larger structures. Unaware Liberty Point had been turned into an elaborate trap, the inexperienced Volunteers blundered straight into it, suffering nearly fifty percent casualties after just under an hour of heavy fighting. At the same time a mix of Taurian aerospace fighters and conventional bomber struck at the Magistracy DropShips, cutting off any avenue of escape and prompting the remaining Magistracy troops to surrender rather than be destroyed.  
Thanks to the lack of significant Concordat aerospace forces, Portland was a more conventional battle for the Magistracy's First Canopian Light Horse Regiment, able to secure a landing zone near the town of Carter's Mill, before proceeding to advance and capture the planetary capital of Cooperton after only a brief skirmish. Due to Portland's sparse population and lack of hard targets, the Canopians were content to merely hold Cooperton until they increasingly came under fire by guerilla raids launched by local militia forces. While outnumbered, the Taurian's vastly superior knowledge of their world allowed the smaller force to engage the invaders and evade retaliation with ease. With little of value and unable to make any significant progress against the Taurian insurgents, the Light Horse finally opted to plunder the capital of food and basic supplies before withdrawing to their DropShips. When word followed soon after that ceasefire was being discussed, the Light Horse gladly returned home.  
The sheer speed of the Magestrix's response along with the spectacular failure on Herotitus gave the Taurian government pause. For both sides the heavy loss in men and material prosecuting a conflict multiple jumps from their nearest friendly border rammed home the utter pointlessness of the war and any thoughts in either realm about continuing on quickly faded. In a lowkey ceremony on Detroit in February 2814, the war was settled by a treaty between the Concordat and the Magistracy that was nearly identical to the Star League treaty that had set the border before the conflict, reaffirming Herotitus, Detroit and Spencer as demilitarized systems with prisoners of war returned to their respective homelands in the following month.     
Though he dismissed Marshal Blake-Andrews in a vain attempt to deflect blame for the failed campaign onto her, Semyon Calderon lost almost all of his prestige and influence over his ignominious defeat and the total lack of any Davion aggression (or even interest!) made him a laughing stock in both Periphery realms, local media deriding him for "playing House Lord". With the Privy Council and Taurian people having lost faith in his leadership, Semyon would ultimately resign as Protector in 2816. In his place, the Privy Council chose Minister of Education Rayna Arantino to serve as Protector of the Realm, one of the very few times a member outside of House Calderon has held the post. Blake-Andrews' replacement as head of the TDF was Natal Choudhoury of the Taurian Guard, who would later sum up the war with a dry quip: 'It was not a total loss, it can always be used as a bad example!' While many future Calderon Protectors shared Semyon's paranoia, they would would take this lesson to heart, focusing on internal defense over expansion.     
The Taurian-Canopian War would be the only Periphery war for nearly two centuries; not until the Canopian invasion of the Capellan Confederation in 3030 would any Outer Realm gird itself for a national conflict. Despite the total war tone of the era, the conflict was remarkable as being the "cleanest" of the many border skirmishes of the First Succession War, with no weapons of mass destruction deployed or even WarShip involved. The War was also memorable for exceedingly short time spent fighting, though it stretched for eight months the vast distances between both realms the four battle sites meant bulk of that in total combat operations lasted all of eight Terran Standard days, thus 200 Hour War name used by some observers.    
- While the overall tone of the conflict remains the same, there are notable differences between the first edition The Periphery sourcebook and more recent sources such as the First Succession War sourcebook - the Periphery book has Rockwellawan and Portan rather than Herotitus and Detroit being attacked, offering the alternate name for the conflict as 'Rockwellawan Crisis'. Despite the name changes, events on both sets of worlds remain the same, and as per BattleTechWiki policy the names from the newest source as considered the correct canon choice.
- The Periphery, pp. 61-62 "First Succession War and the Periphery - Concordat-Magistracy War - A Separate War"
- First Succession War, pp. 101-103 "The Succession War (2786-2821) - Hard Times: The Decline of the Periphery - The Taurian-Canopian War (2813-2814)"
- Handbook: Major Periphery States, p.41 "History of the Periphery - Succession War Era"
- The Periphery, 2nd Edition (sourcebook), pp. 10-12 "The Taurian Concordat - Star League and the Succession Wars"
- Field Manual: Periphery, p.48 "Taurian Concordat - The Final Frontier - Succession Wars"
- Field Manual: Periphery
- First Succession War (Source Book)
- Handbook: Major Periphery States
- The Periphery (sourcebook)
- The Periphery, 2nd Edition (sourcebook)
- Start Date - 2813
- End Date - 2813