Foreign Policy Magazine – “As a woman, I can’t go to war and I refuse to send anyone else,” said Rep. Jeannette Rankin, the Montana Republican who famously cast the sole congressional vote against declaring war on Japan following the bombing of Pearl Harbor.

But these days, the old stereotype that women are more dovish than men is much less evident than it was in 1941. In the run-up to the intervention in Libya, commentators noted it was the women in Barack Obama’s administration (Secretary of State Hillary Clinton and U.N. Ambassador Susan Rice, among others) who pushed for military action. And as it turns out, there’s actually some science to this notion: Women legislators remain less likely to send troops off to war than their male counterparts, but female chief executives and cabinet ministers are now more hawkish than men. Call it the Margaret Thatcher effect.

Michael Koch and Sarah Fulton of Texas A&M University examined the national security behavior of 22 democratic countries between 1970 and 2000. They found that a 1 percent increase in the proportion of women in a legislature led to an approximately 0.1 percent decrease in defense spending as a percentage of GDP. And the higher the percentage of female legislators, the less likely the country was to go to war.

But in the executive branch, the results are the opposite. Female chief executives increase a country’s defense spending by an average of more than 3 percent. Female defense ministers preside over 2.5 percent growth in military budgets and their troops are more likely to fight.

So why are women parliamentarians more likely to take after Rankin while those in high office are more likely to emulate hawks like Thatcher? “Female legislators are … more accountable to their local constituency and party,” says Koch. “They’re under less pressure than chief executives to confront gender stereotypes to win races.” But, he says, “executives are expected to take on national security as one of their main responsibilities.”

Koch’s theory also suggests that as female chief executives and cabinet ministers become more common, they might also become less hawkish. But all the same, we’ve come a long way from Rankin to Hillary Clinton.