As the years passed other rival tribes were engaged in battle and were defeated, and these vanquished tribes were allowed to establish their families in the neighbourhood of the victors, thus increasing the heterogeneous population of the settlement. Gradually, the power of Rome spread far and wide, westwards to the sea, eastwards to the Apennines, south towards the lands of the Volsci and north towards the empire of the Etruscans.
Romulus, the inspiration of Rome's victories, disappeared from sight one day when a cloud enveloped him as he was reviewing his soldiers in a thunderstorm on the ground beyond Rome's walls known as the Campus Martius.2 As the cloud lifted and the sun came out again it was seen that the royal throne was empty. There were those who said that the king had been lifted by a whirlwind back to the domain of the gods whence he had come. Others maintained that he had been murdered and his body had been concealed by some of the hundred senators he had created and who were now jealous of his power. But, after a year's interregnum during which the senators shared the government between them, another king was elected; and he in turn was followed by five others. The first of these six kings, all chosen after the necessary omens had been observed, was a learned Sabine and man of peace, Numa Pompilius. He it was who inspired the Romans with their fear of the gods. He appointed priests with specified religious duties and a high priest with wide authority over them, the Pontifex Maximus; he designated virgin acolytes to serve in the shrine of Vesta, goddess of the hearth and fireside, and to attend to her sacred flame; he introduced twelve Salii or Leaping Priests for the service of Mars, giving them a uniform of an embroidered tunic and bronze breastplate and providing them with sacred shields which they were to carry through the city as they chanted their hymns to the triple beat of their ritual dance. He divided the year into twelve lunar months and stipulated certain days upon which it would be unlawful to carry on public business; he built the Temple of Janus, god of gates and doors, which was to be left open when Rome was at war and closed in time of peace.3 And he succeeded in bringing peace to the city by securing treaties of alliance with those neighbouring peoples who were not already bound to it.
Upon Numa's death, however, this peace was disrupted by his royal successor, Tullus Hostilius, who won great glory as a soldier in a reign of thirty-two years. The next king, Ancus Marcius, was a grandson of Numa Pompilius whose noble record in the matter of religious observances he was determined to emulate. Yet Ancus was as ready as Tullus had been to fight for the honour and independence of Rome, provided that wars were declared and peace negotiations conducted in accordance with those strict legal formalities and unvarying rites which were later to be supervised by the priestly representatives of the Roman people, the fetials.
During Ancus's reign a clever, ambitious and cunning young man from Etruria came south to settle in Rome. The grandson of an exile from Corinth, he adopted the name of Lucius Tarquinius Priscus and within a few years had gained for himself so eminent a reputation in the city that he was able to secure his election to the throne on Ancus's death. As king, Lucius Tarquinius Priscus planned the Circus Maximus,4 bringing down horses and boxers from Etruria to entertain the Romans in splendid public games; he enclosed the city within a new, strong wall; he drained the low-lying land where the city's Forum5 stood, making grants of land around this traditional meeting-place to builders of houses, shops and porticoes; and he laid the foundations for a new temple dedicated to Jupiter on the hill known as the Capitol.6
Sometime in about 579 B.C. this first Etruscan king of Rome was murdered by assassins hired by Ancus's who hoped to attain the succession for themselves. But, by concealing her husband's murder, the widowed queen was able to persuade the populace to accept her son-in-law, Servius Tullius, as regent, and eventually as king, entitled to wear the white and purple robe of royalty and to be preceded by lictors, members of the now traditional royal escort each of whom bore before him an axe bound with rods, symbolic of the king's power to beat and behead recalcitrant citizens without trial.
Once established in power, Servius Tullius began the great work for which he was always to be remembered, the organization of Roman society according to a fixed scale of rank and fortune. From now on, a census of the population was to be taken regularly, and the people, already divided into curiae for voting purposes, were to be further divided into various classes and assigned, according to their means, responsibilities in war and privileges in peace. The richest citizens were required to constitute the cavalry, the equites, or, as leaders of the infantry, to equip themselves with sword and spear as well as armour. The rest of the infantry was furnished by four other classes of citizens, the poorer of whom had merely to arm themselves with slings and stones. The poorest citizens of all were exempt from military service, but denied the political privileges which the other classes enjoyed in proportion to their rank.
Having thus organized Roman society in a class system based upon wealth, Servius Tullius then divided Rome into separate administrative areas. He also extended the boundaries of the city, taking in two other hills, the Quirinal and the Viminal, building a rampart around them and, beyond this rampart, distributing land which had been captured in war among ordinary citizens. This distribution much displeased the Senators and, in their discontent, Servius's rival, Tarquin, son of the murdered Lucius Tarquinius Priscus, saw his opportunity to replace him. Encouraged by his wicked and ambitious wife Tullia, Tarquin increased his influence in the Senate by promises and bribery and, when he considered the time ripe, he had Servius murdered. Tullia triumphantly drove over the corpse in her carriage, spattering her dress with blood. And so, in about 534 B.C., the tyranny of Tarquin the Proud began.
Declaring that an idle people was a burden on the state, he inaugurated a massive programme of public works, lavishing the spoils of a successful campaign against the Volscians upon the enlargement and adornment of the magnificent Temple of Jupiter which his father had begun, and setting to work upon it not only builders and craftsmen from all over Etruria but also hundreds of labourers from the proletariat of Rome. Work also began on improvements to the Circus where new tiers of seats were constructed, and upon the excavation of the Cloaca Maxima, the great sewer of the city.7