Final answer:
Martin Luther's speech was addressed to Emperor Charles V at the Diet of Worms in 1521, where he refused to recant his challenges to the Catholic Church.
Step-by-step explanation:
Martin Luther addressed his speech to Emperor Charles V during the Diet of Worms in 1521. Luther was summoned because of his Ninety-five Theses and other writings, in which he had challenged the Catholic Church's practices, such as the sale of indulgences, and asserted that salvation is achieved through faith alone, not by purchasing indulgences or performing good works. His refusal to recant led to his excommunication and intensified the Protestant Reformation, a movement aiming to reform the Catholic Church's practices and doctrines. The two Habsburg dynasties remained allied until the extinction of the Spanish line in 1700. In 1557, Charles retired to the Monastery of Yuste in Extremadura and died there a year later.