Of locusts and leeches

In this paragraph Cicero considers the impact the presence of an army has on the wider population, both within Italy and beyond. In his effort to rouse sympathy with the plight of allies and external nations affected by warfare or, more specifically, undisciplined or marauding troops owing to a lack of leadership, he encourages his audience to draw on recent personal experiences. We get the following three scenarios:

• (i) Roman armies on the march through Italy (itinera)
• (ii) Roman armies attacking enemy cities (hostium urbes)
• (iii) Roman armies camping in their winter quarters (hiberna, sc. castra) among allied nations (sociorum civitates)

In what is prima facie a highly counterintuitive argument (phrased carefully, to be sure, in the form of a rhetorical question), Cicero implies that (i) and (iii) have caused greater havoc than (ii). The ‘collateral damage’ caused by troop movement within Italy (cf. in Italia) serves as basis for his suggestion that outside Italy (cf. apud exteras nationes) the destructive impact on allied nations (sociorum civitates) by Roman winter quarters exceeds the harm done to enemies (cf. hostium) by Roman soldiers sacking their cities. This is baffling – and prepares for the explanatory punch-line set up by enim. The reason for this unfortunate paradox is that soldiers tend to plunder their host community into ruin unless their general checks their marauding; but only a general who exercises self-control (a rare creature indeed, so Cicero implies) is able to control his army.