The conflict known as the Battle of Ylesia erupted following a joint raid by the New Republic and the Chiss Ascendancy on Ylesia during the Yuuzhan Vong War. A substantial fleet, commanded by Admiral Traest Kre'fey and incorporating Jedi elements like the notorious Kyp's Dozen and the celebrated Rogue Squadron, had been stationed near Kashyyyk. For several months, this fleet engaged in hit-and-run operations, targeting vulnerable points in the Yuuzhan Vong lines. Jedi Master Kyp Durron received information indicating that the Ylesian Republic had been established on Ylesia, formerly a slave world controlled by the Hutt.
Initially, Durron and Kre'fey favored a swift and devastating assault on the planet. Their aim was to obliterate everything as a demonstration of the consequences for collaboration, a feat easily achievable given the Ylesian garrison's small size and poor coordination. However, Jacen Solo suggested capturing the leadership for trial, a move intended to provide a much-needed morale boost to the New Republic and divert the attention of the HoloNet from the war's unfavorable progress.
Concurrently, Thrackan Sal-Solo, the diktat of Corellia and leader of the Centerpoint Party, was compelled by Supreme Overlord Shimrra to assume the presidency of both the Peace Brigade and the Ylesian Republic. This appointment was in exchange for Corellia's protection from Yuuzhan Vong attacks. A small Yuuzhan Vong force, under the command of Supreme Commander Maal Lah, arrived on Ylesia to oversee the Ylesian military. Simultaneously, Pwoe, the claimant to the title of Chief of State of the New Republic, arrived to negotiate a "peace treaty" between the New Republic and the Ylesian Republic.
The New Republic forces were divided into three groups and included Interdictor cruisers to prevent enemy ships from escaping. The Peace Brigade forces, largely composed of New Republic warships and starfighters captured in earlier battles, were swiftly defeated with minimal New Republic casualties (approximately half the fighter pilots were inexperienced rookies). Meanwhile, Jedi Knight Jaina Solo and General Tigran Jamiro led a ground team into the Ylesian capital, Peace City, where they successfully captured the entire Ylesian Senate, including Pwoe and Sal-Solo.
Their retreat was interrupted by an ambush by Yuuzhan Vong warriors and the arrival of a Yuuzhan Vong reinforcement fleet. However, Colonel Jagged Fel's command of Vanguard Squadron and Twin Suns Squadron facilitated the evacuation of the prisoners and soldiers with minimal losses. The New Republic fleet safely returned to Kashyyyk, and the Peace Brigaders were subsequently put on trial.