When Francesco Maria returned to the camp, the imperialists, who had passed the Trebbia on the 20th of February, were slowly advancing through the ecclesiastical state of Modena upon Bologna. His tactic was to place them between two hostile armies; so the Marquis of Saluzzo, with the French, ecclesiastical, and Swiss troops, preceded them, leaving garrisons in the principal places, the Duke following with the Venetians, some thirty miles in their rear. Against this plan, which Guicciardini designates a strange proceeding, and which even Baldi most justly criticises, the other leaders vainly protested, alleging, among other reasons, that whilst the army in advance must be speedily weakened by detaching garrisons, the Venetians would probably hang back when their own frontier was freed from danger. News of the truce between the Pope and the Viceroy now arrived, and the Duke, disgusted at this new proof of Clement's fickleness, and indifference to his allies' interests, withdrew his army across the Po. But the courier who brought the treaty to Bourbon at Ponte-Reno, with an order to obey its provisions, was nearly cut to pieces by his troops, infuriated at this interference with their hopes of booty, and the Constable refused to abide by it. The fresh jealousy of their unstable ally, thus suggested to the Venetians, afforded their leader a new apology for not exposing their troops in a general action for the preservation of Bologna. But when Bourbon had passed by that city towards Romagna and Urbino, somewhat more spirit was infused into his movements, as the danger seemed to approach his own frontier. He immediately sent forward two thousand men to protect the duchy, and desired his family to be removed for safety to Venice. On the 5th of March he had struck his camp at Casal-Maggiore, and proceeded in pursuit of the enemy. On that day they passed under Imola, which, with the other cities, was garrisoned by detachments of Saluzzo, in accordance with tactics already explained. Bourbon now scoured the plains of Romagna in search of plunder, skirmishing occasionally with the French division. When at Meldola on the 14th he bethought him of a descent upon Siena, whose old Ghibelline and anti-Florentine preferences promised him a welcome. He, therefore, penetrated the Apennines by forced marches up the passes of the Bidente, and on the 18th reached S. Pietro in Bagno, burning and pillaging as he went.
When the Constable's refusal to accept the treaty was known at Rome, Clement, more perplexed than ever, besought Lanoy to hurry on and induce him to a halt, or at all events to withdraw the Spaniards and men-at-arms from his command. To this the Viceroy with much apparent zeal consented; but doubts have been thrown on his sincerity, for both he and Moncada, whilst professing cordial co-operation with the Pope, are suspected of having secretly stimulated Bourbon's advance upon Rome, as the only means of appeasing the troops, trusting that the grandeur of the enterprise would, in their master's eyes, readily excuse its criminality. It seems doubtful whether Lanoy actually met the Constable; and his mission was understood to have exposed him to great personal risk from the lawless and ungovernable troops. He at all events conveyed to Bourbon a proposition for the immediate payment to his army of 80,000 ducats, with 60,000 more during May, on condition of their retreat within five days; these sums to be advanced by Florence, on the Viceroy's guarantee for repayment of one-half by the Emperor. The direct object of this proposal was to divert the impending storm from Tuscany; and it was fully sanctioned by Clement, true to the policy of Medicean pontiffs, who ever regarded Florence as their patrimony, Rome as their life-interest. In the negotiations to which it gave rise there was a double difficulty. Whilst the demands of a mutinous and starving army were paramount to all other considerations, each party of the confederates struggled to throw upon another the burden of meeting them. The same selfishness sought individual security against the future movements of the general foe, by turning him upon some friendly frontier. The wealthy Florentines lavished their gold to send him back upon Upper Italy, which the timely distribution of a few thousand men in the Apennine gorges might have prevented him from ever quitting. The game of the Proveditore Pisani was to leave no obstacle in the way of his advance in any direction save that of the Venetian terra-firma domain, and to detain the Duke of Urbino with his army of observation as long as possible near that frontier. The French strove at all hazards to keep him clear of their Lombard conquests. The Pontiff, little dreaming of an attack upon his capital, was distracted between the care of Romagna and Tuscany, whilst his fickle imbecility deprived him of all sympathy at his allies' hands; indeed, in this conflict of interests, his pusillanimous tergiversations rendered him the weaker vessel, and he consequently became the chief sufferer. Nor did the Duke of Urbino escape suspicions of bad faith, for he is accused of a secret understanding not to impede Bourbon's descent upon Tuscany, which would naturally liberate his own duchy from danger. Guicciardini, indeed, not only considers revenge for former injuries of the Medici as the key to Francesco Maria's dilatory and inefficient proceedings against the imperialists, but regards his conduct as justified by the provocations received. These sentiments were at all events cherished by the soldiery of Urbino, who wrote "FOR VENGEANCE" upon the houses which they fired on their march through the Florentine territory. Nor were these provocations light, for the grudge which Leo had bequeathed was aggravated by a continued retention of the fortresses in Montefeltro, and still more by an investiture of the entire duchy, granted in 1525 by Clement, in total defiance of the della Rovere rights, to Ascanio Colonna, whose claims we have already considered.[310] This grant, though virtually annulled by the same Pope's subsequent confirmation of the reinvestiture given to Francesco Maria by Adrian VI., gave rise to renewed anxieties on his part about two years later, and it was not until 1530 that we shall see them finally extinguished by the Duke's generous hospitality to his rival.
On the 22nd of April the Constable, finding the mountain peasantry exasperated to a dangerous pitch by the merciless rigours of his lawless soldiery, and his own sanguinary nature being goaded by their ribald taunts, cut short these miserable intrigues by advancing into Tuscany.[*311] The confederate leaders, having at length decided on saving Florence, united their divisions, and on the 25th passed the Apennines near the present Bologna road. The Duke now received an offer of his fortresses of S. Leo and Maiuolo, which still remained pledged to that commonwealth. This he answered by general professions, and next day, sending on the army to Incisa to intercept the approach of Bourbon, he proceeded with a band of faithful followers to the Tuscan capital. The republican faction, calculating upon his support, flew to arms and seized the Palazzo Vecchio, while once more the unpopular sway of the Medici trembled in the balance. But the Duke, with a nobility of purpose that goes far to absolve him from suspicion as to his good faith with the Pope throughout this campaign, rejected the temptation of avenging his many wrongs, and, by extraordinary personal exertions, succeeded in quelling the insurrection, and maintaining the established government. Thus, for the first time, the city saw its Palazzo taken without a revolution following. In gratitude for this service his fortresses were immediately given up to Francesco Maria, who in due time received also the thanks of his Holiness. The act for their restitution was signed on the 1st of May, and on the 14th S. Leo was surrendered to his lieutenant Orazio Florido.
Bourbon's head-quarters were meanwhile at Montevarchi, near Arezzo, where, seeing his approach to Florence foiled, and the dissatisfaction of his followers on the increase, he decided upon making a dash at Rome; his only alternative being to lead them to pillage, or perish at their hands. As a blind to the Pope, he sent forward a courier to demand free passage to Naples; and, after receiving some supplies from Siena, he abandoned his artillery and heavy baggage in order to lighten his march. He began it on the 26th, and, notwithstanding incessant rains and an entirely disorganised commissariat, he passed without halt or question by Acquapendente and Viterbo to Rome.[312]