William I, Prince of Orange was shot to death by the French Catholic Balthasar Gerard on July 10, 1584. This assassination stunned Elizabeth I, adding to her fears that Catholic agents could be plotting to kill her.
Reluctantly, she allowed her favorite, Robert Dudley, Earl of Leicester, to take English forces to the Continent in 1585, joining the conflict between Spain and the rebels in the Spanish Netherlands. She was undercutting Leicester from the beginning of his expedition as Elizabeth also arranged secret treaty discussions with Spain days after he landed. She did not want Leicester to engage in battle (incurring costs) and never properly supplied the English troops, leaving them without resources. Leicester resigned his position as Lieutenant-General of the thwarted expedition in 1557.
By the way, Gerard's punishment was swift and severe: "Gérard was caught before he could flee Delft, and imprisoned. He was tortured before his trial on 13 July, where he was sentenced to be brutally — even by the standards of that time — killed. The magistrates decreed that the right hand of Gérard should be burned off with a red-hot iron, that his flesh should be torn from his bones with pincers in six different places, that he should be quartered and disemboweled alive, that his heart should be torn from his bosom and flung in his face, and that, finally, his head should be cut off", according to the wikipedia article cited above.