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AUSTRALIA - In the meltdown of yet another Australian heatwave, the nation's ethnic testosterone has again boiled over.
Last summer it was the beach and Anglo-Celtics versus Lebanese at Sydney's southern suburb of Cronulla: this week it was a Balkan explosion in the unlikely war zone of the Australian Tennis Open in Melbourne.
In a brief, violent spasm at Melbourne Park, young Australians of Croatian and Serbian lineage crashed into each other with sticks, bottles, fists and feet. Australia was appalled.
As at Cronulla last summer, word of the violence to come had raced across the city by SMS text messages. Before Croat and Serb players met on the court, young Croatian men gathered at Federation Square on the banks of the Yarra, letting off flares and pumping themselves up for action.
Alarmed at the similarities with the Sydney violence, Victorian Equal Opportunity and Human Rights Commission chief executive Dr Helen Szoke attacked what she described as intolerable behaviour. "We do not want another Cronulla-like incident in Australia. It's one thing to be passionate and support your team, but using nationalism as an excuse to abuse others is not acceptable."
Acceptable or not, the tensions that erupted at the Tennis Open are a fact of life in Australian cities. And unlike clashes between other ethnic groups, violence between Croats and Serbs is an enduring enmity that has been passed from generation to generation.
Poverty, a sense of alienation and national rivalry among migrant groups have triggered conflicts in a country that has nonetheless blended a vast spectrum of nationalities and cultures into a largely successful multicultural society.
Wars abroad have brought many underlying tensions to the surface - between Jews and Arabs and Greeks and Macedonians, among others.
Testosterone has inflamed passions in marginalised groups, with young men testing manhood by defending ethnicity and beliefs with fists and clubs.
A study of ethnic gangs by the Centre for Multicultural Youth Issues found that groups of young men fought in both schoolyards and on the streets in violence triggered by racism. Most believed they were treated poorly by society and police, claiming harassment and institutional racism.
Other clashes have been turf wars: Vietnamese and Lebanese gangs in Sydney, for example, battling over the drug trade. But while violence between other opposing communities has tended to peak and trough, Serb-Croat rivalry has been a constant.
More than a decade ago, Human Rights and Equal Opportunity produced a landmark study of racist violence in Australia. While it found violence between ethnic groups was not a major social issue for Australia, it noted the reality of anger and said: "The most widespread and violent form of inter-ethnic conflict is reported to be that between Croatian and Serbian people."
Soccer has been a constant flashpoint. Dismayed by continual violence, the Football Federation two years ago dropped teams formed from different ethnic communities and created a new A-League competition with teams representing cities instead.
Even so, when the Croat favourite Sydney United played Serb-backed Bonnyrigg White Eagles, rival fans pelted each other with bottles, cans, sticks and rocks over a wire fence erected to keep them apart.
Their rivalry is deep and ancient, brewing from animosities formed well before the Balkan states emerged from World War II as communist Yugoslavia, and inflamed by that nation's brutal disintegration in the 1990s.
The politics and ethnic divisions of the old country have been nurtured in Australia. Some researchers have also concluded that unlike earlier generations of migrants, Serb-Croat hostilities and nationalistic loyalties have been fostered by television, the internet and cheap and easy travel.
While the mutual hostility of other migrant groups has tended to weaken and even vanish with succeeding and inter-marrying generations of Australian-born children, Balkan divisions have remained, despite efforts on both sides to heal them.
Part of this, at least, has sprung from the nature of Serbian and Croatian migration to Australia, documented in a doctoral dissertation by University of Texas researcher Gregory Scott Brown.
Most of the Croats who arrived in Australia in the huge European exodus after World War II and the following decades loathed Yugoslavia's communist regime. Radical politics of the right were encouraged, and Balkan hostilities transferred.
Despite often violent divisions within the community, hard-liners were active. Ultranationalist groups ran paramilitary training camps in the bush and founded youth groups to ensure militant nationalism was passed on to new generations.
Young Croats today use the symbolism of the wartime Ustache resistance. Serbs carry symbols of Chetnik fighters and of former Serbian royals.
Australian-led Croat groups attempted two unsuccessful uprisings in Cold War Yugoslavia, and within Australia were responsible for assaults, murders, bombings and arsons. Older Croats fostered the belief they were victims of Yugoslavian oppression, encouraging a view - still persisting among some Australian-born Croat youths - that they are Croatians first, Australians second.
The disintegration of Yugoslavia gave new focus to Croatian nationalism, even several generations distant. Some went to fight. Many more helped raise millions of dollars to arm them, or to lobby for recognition of an independent Croatia.
Similar loyalties have persisted among Australia's Serbs: when American warplanes bombed Kosovo, demonstrations erupted around the country, with riot police battling youths in Sydney and Melbourne.
Australian Serbs were dismayed by the bombings. They had earlier felt isolated by perceptions the Balkan tragedy was the fault of Serbia. The loss of Kosovo was another bitter blow.
Scott Brown found that the Australian Serbs who fled Croatia and Bosnia in the mid-1990s formed the bulk of the caseload of Victoria's Foundation for the Survivors of Torture and Trauma.
Many had been beaten with baseball bats and rifle butts by Croat and Bosnian Muslim paramilitaries.
Others were raped or forced to watch the torture of family members. This contributed to high rates of mental illness, suicide and marital discord.
Politically, Serbs were stunned by Australian perceptions: from being wartime allies they were now seen as the aggressors in the Balkans. They formed new organisations to counter that view, but feel they have failed.
Most Australian Serbs also migrated from parts of the former Yugoslavia now in Bosnia-Herzegovina and the Krjina region of Croatia, where old hatreds run deep, and where many wartime Serb families suffered from the Croat Ustache.
They believe they are victims of a highly organised Croat propaganda machine they claim has led to discrimination and anti-Serb Government policies.
Animosities flared with the war at home. Both sides reported shootings, brawls, intimidation, assaults and death threats. Pig heads were impaled on church fences. Churches were regularly attacked. Anger still simmers. Leaders from both communities have condemned the tennis violence, and urged measures to promote harmony.
"Racially motivated abuse and violence is intolerable at sporting events, whether it involves Serbs and Croats at the tennis, Australian and English supporters at the cricket, or incidents at junior soccer level," Dr Helen Szoke said.
"As a community we owe it to ourselves to ensure our efforts to stamp out racial intolerance are not in vain."
