Complex sentence: In 1306, Aachen was given Imperial immediacy and declared a Free Imperial City of the Holy Roman Empire, played a conspicuous part, especially in the league which, between 1351 and 1387, kept the peace between the Meuse and the Rhine.
Split into simpler sentences: In 1306, Aachen was given Imperial immediacy and declared a Free Imperial City of the Holy Roman Empire. Aachen played a important part in the league which kept the peace between 1351 and 1387 between the Meuse and the Rhine.