The Galen border conflict was a border skirmish between the United Federation of Planets and the Talarian government, fought during the late 2350s. It took place over several border planets, including Castal I and Galen IV.

Although technologically inferior to the Federation, the Talarians compensated by a willingness to fight to the death and the employment of unconventional guerrilla warfare tactics. One such maneuver was to send out a general distress call from an abandoned observation craft, rigged with a self-destruct device that employed a subspace proximity detonator. This tactic alone resulted in 219 fatalities over a three day period.

In 2357, the Federation colony on Galen IV was overrun and destroyed by Talarian forces, who saw the Federation colonists as encroaching on their territory. There was only one survivor: a four-year-old Human boy named Jeremiah Rossa. His parents had been killed, and Jeremiah was adopted by the Talarian captain Endar, who had led the attack. Endar, who lost his own son earlier at Castal I, had acted on a quid pro quo basis in accordance with Talarian tradition.

Eventually, a peace agreement was signed between the two powers, which included the return of all prisoners of war. Relations between the two powers remained cordial until 2367, when Jeremiah was rescued from a disabled observation craft by the USS Enterprise-D.

War nearly erupted again when Endar demanded the return of his adopted son, whom he had named Jono, while Jeremiah's natural relatives wished for him to be returned to the Federation. An armed conflict was averted when Captain Jean-Luc Picard decided to return Jono to the Talarians, since it is that home which he had known most of his life. (TNG: "Suddenly Human")

According to the Star Trek Encyclopedia (4th ed., vol. 1, p. 292), the conflict started over territorial claims by the two factions over the Galen system.
According to the script this was described as "border conflicts" and the deaths caused by their guerilla maneuvers were said to have accumulated over three years, not three days.
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