In Bales's case, the trigger may have been a fourth deployment to a combat zone after three one-year deployments in Iraq since 2003, during which he suffered concussion and lost part of a foot. He also had money problems, but it was Afghans he shot, not bankers. In his mind it was Afghans, Muslims, whatever, who were causing his problems.
Both men had had run-ins with the law: Bales for assault in 2002, Merah for stealing a woman's handbag in 2007. But Merah spent two years in prison for the mugging, and while there, as is often the case with teenage Muslim thugs, he was converted to the extremist Islamic ideology called Salafism.
Merah videotaped his attacks, so we know that just before he shot his first victim, an unarmed French paratrooper, Merah told him: "You kill my brothers, I kill you." He was an unemployed small-time criminal with delusions of grandeur, and he wanted to "bring the French state to its knees" in retaliation for French participation in America's war in Afghanistan. His claim to belong to al-Qaeda, however, was probably just a private fantasy.
Predictably, Marina Le Pen, leader of the extreme right National Front, called on French voters to "fight ... against these politico-religious fundamentalists who are killing our Christian children, our Christian young men." (She is running in next month's presidential election.) The incumbent right-wing president, Nicolas Sarkozy, says much the same thing, but less bluntly.
Yet two of the three paratroopers Merah killed were Muslims. The other dead soldier, a Christian of West Indian origin, just had the bad luck to be in the street with two Muslim comrades when Merah found them. (He was deliberately targeting French Muslim soldiers as traitors to his cause.)
Merah was hunting another Muslim soldier when he found himself outside a Jewish school and seized the chance to murder a young rabbi, his 5- and 3-year-old sons, and 8-year-old Myriam Monsonego. It was a monstrous act, but in his disordered mind he believed that he was taking revenge for the Muslims who had been killed in the wars in Afghanistan and Iraq.
It's no excuse, but it is an explanation. And the more relevant fact is that only one out of perhaps two million young Muslim French males has committed such an atrocity. What happened is appalling, but it is statistically insignificant. It should also be politically insignificant, but that may be too much to ask in the midst of a presidential election campaign.
The United States is also heading for a presidential election this year, but the only role the war in Afghanistan has in the campaign is ritual accusations by Republican candidates that President Obama is "soft on terror". (On the contrary, he has become the willing prisoner of the Washington foreign policy consensus that still defends the profoundly misconceived Afghan adventure.)
As for the Bales atrocity, it is already being written off by the American media and public as a meaningless aberration that tells us nothing about US foreign policy or national character. Not so. It tells us that the character of American soldiers is no better or stronger than anybody else's, and it is a reminder that 10 years occupying a foreign country will make any army hated from without and rotten within.
The army will become even more demoralised and undisciplined if it is a professional force that rotates the same soldiers through repeated combat tours with no visible success on the horizon. Recent instances of American soldiers urinating on dead Taleban fighters and burning Qurans are symptoms of the same malaise that finally drove Bales around the bend. Obama should not wait until 2014. It's time to go home.
Gwynne Dyer is a London-based independent journalist whose articles are published in 45 countries.
