The next event in the struggle was a conspiracy of Leopold of Austria with Charles IV. of France, favored by the Pope, to overthrow Ludwig. But the other German princes who were concerned in it quietly withdrew when the time came for action, and the plot failed. Then Ludwig, tired of his trials, sent his prisoner Frederick to Leopold as a mediator, the former promising to return and give himself up, if he should not succeed. Leopold was implacable, and Frederick kept his word, although the Pope offered to relieve him of his promise, and threatened him with excommunication for not breaking it. Ludwig was generous enough to receive him as a friend, to give him his full liberty and dignity, and even to divide his royal rule privately with him. The latter arrangement was so unpractical that it was not openly proclaimed, but the good understanding between the two contributed to the peace of Germany. Leopold died in 1326, and Ludwig enjoyed an undisputed authority. [Sidenote: 1327. QUARREL WITH THE POPE.] In 1327, the Emperor felt himself strong enough to undertake an expedition to Italy, his object being to relieve Lombardy from the aggressions of Naples, and to be crowned Emperor in Rome in spite of the Pope. In this, he was tolerably successful. He defeated the Guelphs and was crowned in Milan the same year, then marched to Rome, and was crowned Emperor early in 1328, under the auspices of the Colonna family, by two excommunicated Bishops. He presided at an assembly of the Roman people, at which John XXII. was declared a heretic and renegade, and a Franciscan monk elected Pope under the name of Nikolaus V. Ludwig, however, soon became as unpopular as any of his predecessors, and from the same cause--the imposition of heavy taxes upon the people, in order to keep up his imperial state. He remained two years longer in Italy, encountering as much hate as friendship, and was then recalled to Germany by the death of Frederick of Austria. The Papal excommunication, which the Hohenstaufen Emperors had borne so easily, seems to have weighed sorely upon Ludwig's mind. His nature was weak and vacillating, capable of only a limited amount of endurance. He began to fear that his soul was in peril, and made the most desperate efforts to be reconciled with the Pope. The latter, however, demanded his immediate abdication as a preliminary to any further negotiation, and was supported in this demand by the king of France, who was very ambitious of obtaining the crown of Germany, with the help of the Church. King John of Bohemia acted as a go-between, but he was also secretly pledged to France, and an agreement was nearly concluded, of a character so cowardly and disgraceful to Ludwig that when some hint of it became known, there arose such an angry excitement in Germany that the Emperor did not dare to move further in the matter. [Sidenote: 1338.]