During the 150 years following the Reunification War, the far-flung territories of the Star League experienced a new wave of scientific innovation and colonial expansion. To reduce the administrative problems caused by lengthy interstellar-communication lags, the Star League developed a vast and intricate network of communications relay stations employing FTL transmitters. Known as hyperpulse generators (HPGs), these transmitters were developed from technology based on Kearny-Fuchida hyperdrive principles. Research begun in 2615 came to fruition 15 years later when the first HPG message was successfully transmitted from Terra to the Lyran Commonwealth. The HPG was essentially a large "gun" that fired a high-frequency compressed pulse through K-F space at a target world. The pulse traveled the immense distance instantaneously, just like a faster-than-light spacecraft. Though the energy cost for a single transmission was of the same magnitude as for a jump by an FTL ship, an HPG pulse could travel up to 50 light years, while a ship could jump a maximum of 30 light years. When completed, the system effectively cut the average communication time between Terra and the Periphery from more than a year to about six months. Communications time could be cut to days, but only at great cost.

          At the same time, League engineers developed a new, low-cost water- purification system. It was significantly cheaper to operate this system than to import water, making it economically feasible to settle Inner Sphere worlds previously ignored during the Exodus. The system also provided many settled worlds with an unexpected economic boom. The Ryan Cartel, the great iceship manufacturer and operator, was nearly driven bankrupt as fewer and worlds relied on its service. By 2700, more than a thousand new worlds had been settled, and the Star League had expanded to control a sphere roughly 540 light years in diameter.

          In a final important development, engineers working to improve BattleMech mobility were able to develop an improved, more efficient myomer. This improvement finally made it possible to construct artificial "bionic" limbs of human size, as well as full-scale, super-string human exoskeletons for use in industry.

          Spurred by the adoption of a universal currency and the removal of the artificial trade barriers imposed by the Age of War, trade and commerce also boomed. As prosperity grew, Star League worlds became increasingly independent. With development and transportation costs low, many planets developed highly specialized economies that made them dependent on other worlds for basic commodities such as food, water-purification equipment, and replacement parts.

          Only on major political crisis occurred during this golden age, and it was resolved fairly easily. In 2650, reports reached Terra that Tadeo Amaris, leader of the Rim Worlds Territorial-State, was expanding his personal army at an alarming rate. Michael Cameron, having recently succeeded to the title of First Lord of the Star League, convened a special meeting of the Star League High Council, whom he persuaded to issue an edict restricting te size of personal military forces that any League member could raise. To back up this administrative action, Cameron gave Amaris a warning by sending several Star League Defense Force BattleMech regiments to conduct extended maneuvers just beyond the boundary of the Rim Worlds. Shortly after, League intelligence confirmed that Amaris had apparently disbanded his extra regiments. In truth, Amaris and other state leaders continued in secret to strengthen their militia and reserves. Though the Star League represented apparent unity among the stars, member-states continued to fight "Hidden Wars" during this "golden age" of peace and prosperity.