The great war with Etruria--which possibly, moreover, has been placed so close upon the expulsion of the Tarquins only in consequence of chronological confusion in the Roman annals--cannot be regarded as an intervention of Etruria in favour of a countryman who had been injured in Rome, for the very sufficient reason that the Etruscans notwithstanding their complete victory neither restored the Roman monarchy, nor even brought back the Tarquinian family.
Powers of the Consuls If we are left in ignorance of the historical connections of this important event, we are fortunately in possession of clearer light as to the nature of the change which was made in the constitution.

The royal power was by no means abolished, as is shown by the very fact that, when a vacancy occurred afterwards as before, an "interim king" (-interrex-) was nominated.

The one life-king was simply replaced by two year-kings, who called themselves generals (-praetores-), or judges (-iudices-), or merely colleagues (consules).( 3) The principles of collegiate tenure and of annual duration are those which distinguish the republic from the monarchy, and they first meet us here.
Collegiate Arrangement The collegiate principle, from which the third and subsequently most current name of the annual kings was derived, assumed in their case an altogether peculiar form.

The supreme power was not entrusted to the two magistrates conjointly, but each consul possessed and exercised it for himself as fully and wholly as it had been possessed and exercised by the king.

This was carried so far that, instead of one of the two colleagues undertaking perhaps the administration of justice, and the other the command of the army, they both administered justice simultaneously in the city just as they both set out together to the army; in case of collision the matter was decided by a rotation measured by months or days.