The popes who immediately preceded Gregory had more than once forbidden the churchmen to receive investiture from laymen. Gregory reissued this prohibition in 1075,[111] just as the trouble with Henry had begun. Investiture was, as we have seen, the legal transfer by the king, or other lord, to a newly chosen church official, of the lands and rights attached to the office. In forbidding lay investiture Gregory attempted nothing less than a revolution. The bishops and abbots were often officers of government, exercising in Germany and Italy powers similar in all respects to those of the counts. The king not only relied upon them for advice and assistance in carrying on his government, but they were among his chief allies in his constant struggles with his vassals. [Sidenote: Henry IV angered by the language of the papal legates.] Gregory dispatched three envoys to Henry (end of 1075) with a fatherly letter[112] in which he reproached the king for his wicked conduct. But he evidently had little expectation that mere expostulation would have any effect upon Henry, for he gave his legates instructions to use threats, if necessary, which were bound to produce either complete subjection or out-and-out revolt. The legates were to tell the king that his crimes were so numerous, so horrible, and so notorious, that he merited not only excommunication but the permanent loss of all his royal honors. [Sidenote: Gregory VII deposed by a council of German bishops at Worms, 1076] The violence of the legates' language not only kindled the wrath of the king but also gained for him friends among the bishops. A council which Henry summoned at Worms (in 1076) was attended by more than two thirds of the German bishops. Here Gregory was declared deposed owing to the alleged irregularity of his election and the many terrible charges of immorality and ambition brought against him. The bishops renounced their obedience to him and publicly declared that he had ceased to be their pope. It appears very surprising, at first sight, that the king should have received the prompt support of the German churchmen against the head of the Church. But it must be remembered that the prelates owed their offices to the king and not to the pope. In a remarkable letter[113] to Gregory, Henry asserts that he has shown himself long-suffering and eager to guard the honor of the papacy, but that the pope has mistaken his humility for fear. "Thou hast not hesitated," the letter concludes, "to rise up against the royal power conferred upon us by God, daring to threaten to deprive us of it, as if we had received our kingdom from thee. As if the kingdom and the Empire were in thine and not in God's hands.... I, Henry, King by the grace of God, together with all our bishops, say unto thee, come down, come down from thy throne and be accursed of all generations." [Sidenote: Henry IV deposed and excommunicated by the pope.]