Second Telom War

The Second Telom War or 20 Years' War was an interstellar war between the Ur-Han and the rest of the known galaxy's nations. It lasted from 2168 to 2188. It marked a shift in the balance of powers in the galaxy. The Ur-Han emerged victorious and would remain the main galactic power for over a century. 
The war began in 2168, following a border skirmish between a Telom fleet and an Ur-Han border patrol. The Telom fleet captured four Ur-Han ships and their crews. The crews were humiliated on Telom national television. This sparked outrage among the Ur-Han public, and a month later war was declared. The Ur-Han had built up their military more than any other nation. The Ur-Han navy is estimated to have representeted at the time half of all military ships in the galaxy. The Ur-Han came to a similar position as in the First Telom War, and got in orbit of the Telom homeworld. Unlike the previous time however, the Ur-Han started bombing the planet. This led to over 1.2 billion deaths, in a population of only 3 billion. The Ur-Han ignored the peace proposals of the Telom and continued to bomb them. This continued until 2176, when the Surben and Mirdesh jointly declared was on the Ur-Han. This came as a surprise to many within the Ur-Han military, as they hadn't expected the Mirdesh to join the war. The Mirdesh border was very close to the Ur-Han homeworld, and their navy was forced to leave Telom space. The Surben navy liberated most of the Telom Nation whilst the Mirdesh navy closed in on the Ur-Han homeworld. 
Seemingly overwhelmed, the Ur-Han decided to attempt an offensive on the Mirdesh homeworld, rather than to defend their own. Their gamble paid off, and by 2178, the Ur-Han forces, whilst pushed back to their space had managed to kick all foreign forces out. The Mirdesh would however find themselves in a series of internal conflicts, known as the Jadim Wars from 2179. The Mirdesh decided to sign a separate peace with the Ur-Han, ceding four inhabited systems, with seven planets. The Telom had by now recreated a substantial military force, and with the Surben attempted to make a decisive blow to the Ur-Han to knock them out of the war for good. However, their combined forces were defeated in the Battle of Canina Majoris in 2182, where Ur-Han forces utilized their numerical superiority and greater strategic knowledge to all but wipe out the combined Surben-Telom fleet. The Ur-Han were presented with a peace deal, but decided to press the attack. In 2185 they had secured Telom space, the Telom having by now been completely exhausted by the conflict. The Telom capitulated and were annexed in the following year. The two last years of the conflict included multiple planetary invasions, blockades and bombings of Surben planets by Ur-Han navies. The Surben capitulated in October 2188. 
Unlike the first, the Second Telom War had a tremendous geopolitical impact. The Ur-Han saw their number of planets doubled, having annexed over 30 worlds. The Mirdesh Confederacy and Surben Republic, saw their relations worsened by the Mirdesh separate peace. The Mirdesh Confederacy was greatly weakened, with the Jadim Wars lasting another 15 years. Regions affected by the Jadim Wars are still affected by terrorism and insurgencies to this day, and are the main focus point of UCO peacekeeping operations. The Mirdesh's beliefs of peaceful expansions were permanently shattered. During and after the Jadim Wars, Mirdesh started incorporating other species through outright military conquest. This was in stark contrast with their exclusively diplomatic approach so far. The Surben Republic entered an era known as the Century of Shame. Until the First Contact War, the Surben were in a state of perpetual economic and political crises, one after another. This even saw the appearance of the first and only dictatorship in Surben history, the Five Year Marshallship, from 2246-2266 (the Five Year designation comes from the Surben calendar, with Surben years being roughly equivalent to 4 Earth Standard Years). The Telom were definetly wiped out as a major galactic nation, and have since then never been independent again. The Telom's homeworld was permanently damaged during the war, and the capital of the newly formed Telom Duchy would be moved to another planet in 2201. The Ur-Han became a galactic superpower by the end of the war. Some Terran and Surben scholars even believe the Ur-Han became the first galactic hyperpower. The Ur-Han saw their number of worlds doubled and population nearly tripled. They enjoyed a period of prosperity known as the Ur-Han Golden Age, which coincides with the Surben Century of Shame. The Golden Age saw a tremendous amount of artistic creation, with some of the Ur-Han's greatest literary pieces being written at this time. The greatest of which are regrouped in the so-called Eight Classics. It is at this period the Third Royal Palace was built on their homeworld. The project took sixty years to complete, and would remain the royal residence up until the Great War. It has since been reconverted into a museum, and today is one of the most visited buildings in the galaxy, for its magnificent mosaics and paintings. 
One major consequence of the war was the acceleration in FTL developments. Up to the beginning of the war, FTL drives had been pretty stagnant, their speeds increasing only about 30% from their original speeds. The war saw many operations decided by the tremendous travel times necessary to deploy a force. The following decades saw the speed of FTL drives doubled, and it would be doubled again by the end of the century. The speeds would then stagnate again up until the last few decades (mainly since the 2680s), when Terran scientists started extensively reexamining topic.