The historical event associated with the trial and execution of Charles I was the English Civil War and the subsequent establishment of the Commonwealth. Following a power struggle between the monarchy and Parliament, Charles I was perceived as a tyrant and was ultimately tried for treason in 1649. His execution marked the first time a reigning monarch was sentenced to death by his own government, representing a pivotal moment in British history. The event challenged the divine right of kings and set a precedent for future governance, leading to increased parliamentary power and the eventual restoration of the monarchy in 1660.