Nicholas Kristof writes: More Americans die in gun homicides and suicides in six months than have died in the last 25 years in every terrorist attack and the wars in Afghanistan and Iraq combined.

So what can we do? A starting point would be to limit gun purchases to one a month, to curb gun traffickers. Likewise, we should restrict the sale of high-capacity magazines so that a shooter can’t kill as many people without reloading.

We should impose a universal background check for gun buyers, even with private sales. Let’s make serial numbers more difficult to erase, and back California in its effort to require that new handguns imprint a microstamp on each shell so that it can be traced back to a particular gun.

“We’ve endured too many of these tragedies in the past few years,” President Obama noted in a tearful statement on television. He’s right, but the solution isn’t just to mourn the victims — it’s to change our policies. Let’s see leadership on this issue, not just moving speeches.

Other countries offer a road map. In Australia in 1996, a mass killing of 35 people galvanized the nation’s conservative prime minister to ban certain rapid-fire long guns. The “national firearms agreement,” as it was known, led to the buyback of 650,000 guns and to tighter rules for licensing and safe storage of those remaining in public hands.

The law did not end gun ownership in Australia. It reduced the number of firearms in private hands by one-fifth, and they were the kinds most likely to be used in mass shootings.

In the 18 years before the law, Australia suffered 13 mass shootings — but not one in the 14 years after the law took full effect.