Don't I look like Caesar at this angle?

The Roman general was invoked by Mussolini to legitimate his rule, but he is also cited as a warning against imperialism. Maria Wyke considers the continuing uses and abuses of Caesar's legacy.

On March 15 every year, spring flowers are placed ceremoniously at the feet of a bronze statue of Julius Caesar that stands in the heart of Rome. Even though, for centuries, Italians have held a toast to Caesar on the Ides of March, this particular ritual dates back only as far as the 1930s. The second decade of the fascist regime was, for its leader Mussolini, "an epoch that can call itself Caesarian, dominated as it is by exceptional personalities who reassume in themselves the powers of the State, for the well-being of the people, against the parliamentarians, just as Caesar marched against the senatorial oligarchy of Rome".

In 49BC, the Roman dictator led his army across the river Rubicon (which divided republican Italy from its provinces) and thus initiated an act of mutinous revolt against the senate. Mussolini drew on this famous incident as glorious legitimation for his own seizure of power and the establishment of a modern dictatorship. Everywhere the Duce and Caesar were favourably compared, down to the supposed similarity of their profiles: the same hawk-eye, the same magnetic glance. And so the yearly adoration of the Roman dictator was ordered to encourage in participants an equal adoration of their 20th-century dictator.

The whispering of Caesar's name in Italian politics continues to this day.

Giulio Andreotti was regularly hailed as "the divine Julius" during his seven terms of office as prime minister, although he was reduced to the status of "a little Caesar" when he fell from grace in the 1990s on charges of collusion with the Mafia. And current prime minister Silvio Berlusconi appealed to Caesar as one of his political models.

But it is not just in Italian politics that this famous Roman statesman continues to intervene. Associated with a crucial turning point in the history of western civilisation (from republic to empire, from elected representation to hereditary monarchy), Caesar quickly took on monumental, almost mythic, proportions. From the time of his own somewhat spare accounts of himself, his life became a hugely valuable resource through which to support or challenge conquest and imperialism, revolution, dictatorship, monarchy and, of course, assassination.

Caesar's commentaries on the Gallic war (written in the third person as if dispatched in haste to Rome from the front line, and famously opening "all Gaul is divided into three parts") are a relentlessly self-aggrandising account of incredible marches, frightful battles, trying sieges and a whole continent discovered, penetrated and put down. Widely circulated from antiquity, they became documents of Caesar's military excellence. At the beginning of the 16th century, in The Art of War , Machiavelli celebrates the Roman general's great strategic choices (exploiting victory to the full, valuing infantry) and his great tactical skill (how to pick the most favourable place and time for an attack). Nowadays, enthusiasts can even replay the siege of Alesia or the surrender of Vercingetorix in computer games.

From the mid-19th century, however, a strong counter-narrative arises of Caesarean ambition, greed, cruelty and genocide. A mass of French works reinterpreted Roman Gaul in the terms of modern France, stressing the importance of resistance against occupying powers. Goscinny and Uderzo, creators of the fictional hero Asterix, drew on this nationalistic tradition to shape the volumes of cartoons that they produced between 1961 and 1983, read by millions of children (and their parents). Asterix humorously symbolises the struggle for political independence, while the omnipresent Caesar is ridiculed as the arrogant imperialist.

Caesar has also been used extensively as a model for good and bad governance. At the beginning of the 19th century, for example, Napoleon Bonaparte frequently compared himself to Caesar. Coleridge saw through Napoleon early on as a military dictator who was substituting the beloved republicanism of France with a masked despotism, whereas Nietzsche described him as the modern incarnation of the classical ideal of Caesar (the superhuman man of titanic inner strength and discipline who could impose the prerogative of the splendid few over the rights of the lying majority). Despite the devastating criticism of this cult of Caesarism that Marx issued in mid-century, Napoleon III repeated his uncle's emulation of Caesar's politics and was regularly understood as a populist monarch or military demagogue who legitimated all his actions in the name of popular sovereignty but controlled France as if it were a police state.

Jesus Christ has also been equated with Caesar. Because, in the medieval tradition, Caesar oversaw the transition from a pagan to a Christian world, he was often proclaimed God's earthly counterpart and his monarchical rule the type of temporal government that best matched the spiritual rule of the Lord. Now, in contrast, Caesar is being drawn on to cast doubt on the divinity of Christ. According to philosopher and linguist Francesco Carotta, the gospels are a house of cards built misleadingly out of the life and cult of the divine Caesar.

In America, meanwhile, Shakespeare's Julius Caesar has been regularly performed and taught as an "American" play dramatising the New World struggle for liberty and republicanism against Old World tyranny. Caesar embodied the faults of the English king, and Brutus all the courage of an American patriot. In the 20th century, US performances of Caesar's assassination were staged as a warning against the rise in Europe of the dictatorships of Hitler and Mussolini, or even against the growth of Caesarism in the US.

Unsurprisingly, perhaps, Caesar still casts his shadow over modern imperialism today. Again and again, political commentators critical of the US have turned to Rome, and its embodiment Caesar, to warn of the consequences of empire-building. The US is a 21st-century Rome, centralising power in its "emperor", dominating the world, invading new territories. Now that the war against Iraq has started, the Doonesbury cartoon strip suggests the imperialist flavour of US foreign policy by casting any postwar settlement in terms of a pretension to provinces and proconsuls. The Romans are coming.

Maria Wyke is senior lecturer in classics at the University of Reading. A conference on the "Uses and Abuses" of Caesar is being held by the British School at Rome this weekend.