Operation Turning Points: Tortuga and the Fronc Reaches deal with the Fronc Reaches battles against the pirates of the Tortuga Dominion in 3072 and 3088. They're both well written and feature both merc units, the Fronc Reaches militia and the Colonial Marshals facing down the pirates in a homage to classic Westerns. Total Chaos and Jihad Final Reckoning deal with the Taurian invasion of the Federated Suns and its defeat during the Jihad, with Field Manual 3085 and 3145 detailing out the rapid decline of the Taurians until about 3145 or so. Era Digest/Report Dark Ages and Shattered Fortress gives some extra information on the Taurians in the late Dark Age era.
Basically, the Taurians go to war against the Federated Suns, gain the Pleadies Cluster but lose much of their other territory after their rebuilt Warship and military forces are driven off over the Jihad. Even using nukes against the Fed Suns doesn't stop their defeat. Taurus also gets hit by an asteroid from the Word of Blakes's mass driver ship, destroying the capital. Their 3085 leader goes paranoid and through bad mismanagement, the Taurians end up as the fifth most powerful faction in the Periphery til about the 3140s. Their crazy leader is overthrown, and they contonue rebuild and open up trade relations with the Filtvelt Coalition, the Calderon Protectorate, the Fronc Reaches, the Magistracy of Canopus, and the Raven Alliance. By 3146, they've rebuilt to 9 mech regiments or so, and extend a reunification offer via marriage to the Calderon Protectorate.
TL:DR, the TC overextends itself in the Jihad, and takes
about 60 plus years to get back to some form of stability and power.