RIGHT SPEAK: Kurdish Women Fight ISIS on Front Lines: “My bravery shames them.”

When 19-year-old Dilar and her girlfriends learned last spring that a woman who taught at a local school had died fighting Islamic State, they made a pact: They would join an all-female Syrian Kurdish brigade named in the teacher’s honor.

Her unit, the Martyr Warsin Brigade, saw action this summer in a tough battle against the extremist fighters for Ras al-Ayn, a town along the Turkish border. Dilar came away without injury and returned home to a hero’s welcome.

(Caskets holding the bodies of four female Kurdish fighters are carried from a hospital in Suruc, Turkey, to a cemetery near the border with Syria. Andrew Quilty for The Wall Street Journal )

Now, during her downtime, she and her female comrades stride with a swagger through their villages east of the embattled city of Kobani.

“When I walk with my gun, the men who haven’t volunteered keep their eyes down around me,” said Dilar, who didn’t want to give her family name. “My bravery shames them.”

As debate flares in Washington and other capitals about whether the battle against Islamic State can succeed without more boots—even U.S. ones—on the ground, Kurdish women have stepped up to defend their lands in Syria and Iraq. An estimated one-third of the Syrian Kurdish fighters in Kobani are women, fighters and residents say, a figure that mirrors their role in other significant battles across Kurdish territories this year.

The monthlong battle over the city on the Turkish border is straining Islamic State, Kurdish politicians and U.S. officials say, and hampering its overall expansion strategy.

The overriding motivation that Kurds give for fighting the insurgents is to save their ancestral homeland from destruction. Yet many women combatants also cite a more personal crusade. Across the territory in Syria and Iraq that it now controls, Islamic State has reinstituted slavery, prohibited women from working and threatened to kill those Muslims, including Kurds, who don’t adhere to their ideology.

“Islamic State are terrorists, inhuman,” said a 28-year-old female commander of both men and women in Kobani who uses the nom-de-guerre Afsin Kobane.

Ms. Kobane was a kindergarten teacher when she decided last year to join the female unit of the Syrian Kurdish resistance force, known as YPJ. Speaking by telephone from her post in the besieged city on the Turkish border, she said her mixed-gender unit had been fighting for more than a month and was holding a position only a half-mile from Islamic State fighters.