Over time, as Rome's empire grew, the two annual consuls ceased to be enough to command its many armies in the field or administer its many provinces. To solve this problem, it became normal to prorogue the authority of current consuls and praetors beyond their normal terms so they could continue to command in the field. Over time, however, with increasing need for competent generals and administrators, prorogation of magistrates became the norm; and the device was used, increasingly by the assemblies, to grant "imperium" to popular politicians.