Niccolo Machiavelli - Discourses on the First Decade of Titus Livius (Chap. 3.48) lyrics

That on finding an Enemy make what seems a grave blunder, we should suspect some fraud to lurk behind. The consul having gone to Rome to perform certain ceremonial rites, and Fulvius being left in charge of the Roman army in Etruria, the Etruscans, to see whether they could not circumvent the new commander, planting an ambush not far from the Roman camp, sent forward soldiers disguised as shepherds driving large flocks of sheep so as to pa** in sight of the Roman army. These pretended shepherds coming close to the wall of his camp, Fulvius, marvelling at what appeared to him unaccountable audacity, hit upon a device whereby the artifice of the Etruscans was detected and their design defeated. Here it seems proper to note that the captain of an army ought not to build on what seems a manifest blunder on the part of an enemy; for as men are unlikely to act with conspicuous want of caution, it will commonly be found that this blunder is cover to a fraud. And yet, so blinded are men's minds by their eagerness for victory, that they look only to what appears on the surface. After defeating the Romans on the Allia, the Gauls, hastening on to Rome, found the gates of the city left open and unguarded. But fearing some stratagem, and being unable to believe that the Romans could be so foolish and cowardly as to abandon their city, they waited during the whole of that day and the following night outside the gates, without daring to enter. In the year 1508, when the Florentines Avere engaged in besieging Pisa, Alfonso del Mutolo, a citizen of that town, happening to be taken prisoner, was released on his promise to procure the surrender to the Florentines of one of the gates of the city. Afterwards, on pretence of arranging for the execution of this surrender, he came repeatedly to confer with those whom the Florentine commissaries had deputed to treat with him, coming not secretly but openly, and accompanied by other citizens of Pisa, whom he caused to stand aside while he conversed with the Florentines. From all which circumstances his duplicity might have been suspected, since, had he meant to do as he had engaged, it was most unlikely that he should be negotiating so openly. But the desire to recover possession of Pisa so blinded the Florentines that they allowed themselves to be conducted under his guidance to the Lucca Gate, where, through his treachery, but to their own disgrace, they lost a large number of their men and officers.