During the greater part of the republic the consuls were recognized as the heads of the administration abroad as well as at home. It thus became necessary that departments of administration (_provinciae_) should be determined and assigned. The method of assignment varied. The least usual device was for one consul to take the field at the head of an army, while the other remained at home to transact the civil business of state. More often foreign wars demanded the attention of both consuls. In this case the regular army of four legions was usually divided between them. When it was necessary that both armies should co-operate, the principle of rotation was adopted, each consul having the command for a single day--a practice which may be illustrated by the events preceding the battle of Cannae (Polybius iii. 110; Livy xxii. 41). During the great period of conquest from 264 to 146 B.C. Italy was generally one of the consular "provinces," some foreign country the other; and when at the close of this period Italy was at peace, this distinction approximated to one between civil and military command. The consuls settled their departments amongst themselves by agreement or by lot (_comparatio_, _sortitio_), the power of declaring what should be the consular _provinciae_ was usurped by the senate, (see Senate), and a _lex Sempronia_ passed by C. Gracchus, probably in 122 B.C., ordained that the two consular provinces should be declared before the election of the consuls. At this time the consuls entered office on the 1st of January (a practice which commenced in 153 B.C.), and their military command began on the 1st of March. They could hold this military command until they were superseded in the following March, and thus their tenure of power was practically raised to fourteen months. But meanwhile the home officials invested with the imperium had proved insufficient for the military needs of the empire, and the system of prolonging the command (_prorogatio imperii_) had been growing up (see Province). The consul whose command had been prolonged now served abroad as proconsul. It is probable that Sulla in his legislation of 81 B.C. did something to stereotype this system. Certainly the government by pro-magistrates becomes the rule after this period (cf. Cicero, _De natura deorum_, ii. 3. 9; _De divinatione_, ii. 36. 76, 77), although there are several instances of consuls assuming the active command of provinces between the years 74 and 55 B.C. (Mommsen, _Rechtsfrage_, p. 30), and Cicero declares that the consul has a right to approach every province ("consules, quibus more majorum concessum est vel omnes adire provincias," Cicero, _Ad Atticum_, viii. 15. 3). Certainly in theory the provinces were still regarded as "consular," not "proconsular," and were technically, although not practically, held from the 1st of March of the consul's tenure of office at Rome (cf. Cicero, _De provinciis consularibus_, 15. 37; Mommsen, _Rechtsfrage_, _passim_).