Then, in the year 1541, his wife died, leaving him two boys; and he remained until 1543 without coming to any further resolution about his life. At that time, in the month of September, there appeared in San Marino one Signor Gustamante, a Spaniard, sent by his Imperial Majesty to that Republic on some affairs. Giovan Battista was recognized by him as an excellent architect, and at his instance he entered not long afterwards into the service of the most illustrious Lord Duke Cosimo, as engineer. And thus, having arrived in Florence, his Excellency made use of him for all the fortifications of his dominion, according to the necessities that arose every day; and, among other things, the fortress of the city of Pistoia having been begun many years before, San Marino, by the desire of the Duke, completely finished it, with great credit to himself, although it is no great work. Then, under the direction of the same architect, a very strong bastion was built at Pisa. Wherefore, his method of work pleasing the Duke, his Excellency caused him to construct--where, as has been related, there had been built on the hill of S. Miniato, without Florence, the wall that curves from the Porta S. Niccolò to the Porta S. Miniato--the fortification that encloses a gate by means of two bastions, and guards the Church and Monastery of S. Miniato; making on the summit of that hill a fortress that dominates the whole city and looks on the outer side towards the east and the south, a work that was vastly extolled. The same Giovan Battista made many designs and ground-plans of various fortifications for places in the states of his Excellency, and also various rough models in clay, which are in the possession of the Lord Duke. And since San Marino was a man of fine genius and very studious, he wrote a little book on the methods of fortifications; which work, a beautiful and useful one, is now in the possession of Messer Bernardo Puccini, a gentleman of Florence, who learned many things with regard to the matters of architecture and fortification from San Marino, who was much his friend.
Giovan Battista, after having designed in the year 1554 many bastions that were to be built round the walls of the city of Florence, some of which were begun in earth, went with the most illustrious lord, Don Garzia di Toledo, to Monte Alcino, where, having made some trenches, he mined under a bastion and so shattered it, that he threw down the breastwork; but as it was falling to the ground a harquebus-ball struck San Marino in the thigh. Not long afterwards, his wound being healed, he went secretly to Siena and took the ground-plan of that city, and of the earthworks that the people of Siena had made at the Porta Camollia; which plan of fortifications he then showed to the Lord Duke and to the Marchese di Marignano, making it clear to them that the work was not difficult to capture or to secure afterwards on the side towards Siena. That this was true was proved by the fact, the night that it was taken by the above-named Marquis, with whom Giovan Battista had gone by order and commission of the Duke. On that account, then, the Marquis, having conceived an affection for him and knowing that he had need of his judgment and ability in the field (that is, in the war against Siena), so went to work with the Duke, that his Excellency sent Giovan Battista off as captain of a strong company of foot-soldiers; whereupon he served from that day onward in the field, as a valiant soldier and an ingenious architect. Finally, having been sent by the Marquis to Aiuola, a fortress in the Chianti, while disposing the artillery he was wounded in the head by a harquebus-ball; wherefore he was taken by his soldiers to the Pieve di S. Paolo, which belongs to Bishop da Ricasoli, and died in a few days, and was carried to San Marino, where he received honourable burial from his children.
