Editor's Note: CNN is committed to covering gender inequality wherever it occurs in the world. This story is part of As Equals, a year-long series.

Sanaa, Yemen — When Halima's father told her he was planning her wedding, the 12-year-old firmly refused.

"My father married off my sisters, and wants to marry me off by force, but I don't want to get married," said Halima, whose father asked CNN not to use his family's surname.

Child marriage is entrenched in Yemen, a symptom of crippling poverty and a deeply conservative culture. It's a traditional practice preserved in proverbs like, "Marry an 8-year-old girl, she's guaranteed" -- an assurance of a child's virginity. And the country's three-year civil war has only exacerbated the problem. Today, more than two-thirds of Yemeni girls are married off before they reach 18, a staggering leap from half of all girls before the conflict.

But Halima, with her quick laugh and infectious smile, is determined not to be a part of that mounting statistic.

"I'm in the fifth grade. I want to finish school. I want to become a doctor, God willing," Halima told CNN, still dressed in her school uniform -- a forest green abaya and white headscarf.

"Many of my friends in school have been married off."

"One of my friends dropped out and when I asked her why, she said, 'Because tomorrow is my wedding.'"

Halima's father walks her home from school.

It's a fate Halima's sister Kafa was unable to avoid. She was wed to a man 15 years her senior when she was just 13.

"If I had the choice, I would have gone to school and been educated. I didn't want to get married. I was coerced. There was nothing for me in marriage as a child," Kafa told CNN, her face concealed by a veil.

Kafa's husband gave her permission to talk, but he declined to speak with CNN.

Four years and four kids after their wedding day, Kafa, now 17, has many cautioning tales for her sister.

"I suffered so much in each childbirth," she said, speaking at her parents' home in the outskirts of the capital Sanaa -- an hour from where she now lives with her husband and daughters.

Young adolescents face a much higher risk of complications and death in pregnancy than other women, according to the World Health Organization.

"Every delivery was through a surgical operation. I stayed in a hospital bed between seven to 10 days after each," Kafa said.

Kafa feeds her daughters.

Their father, Abdullah, is an unemployed laborer, who -- between children, grandchildren and relatives -- says he has 17 mouths to feed.

Increasingly, fathers like Abdullah are marrying off their daughters to be relieved of the cost of their care -- seeking dowry payments to cope with conflict-related hardships or to pay off debts. Abdullah received a dowry of $2,000 for Kafa.

While he says it's a decision he regrets, it hasn't stopped him from planning Halima's marriage -- though he has yet to select a suitor.

Underneath the shade of a green tarpaulin covering the courtyard of their home, Abdullah squats next to Kafa as she feeds her daughters and brushes their hair.

"I want you to forgive me for marrying you at such a young age," he told Kafa. "I needed money to support our family. I married you so that your sisters and mother can live. So I was forced to choose. Now, I am asking for your forgiveness."

Many Yemeni parents are facing this stark reality: collect dowries for their daughters to pay for food and healthcare, or let their other children suffer.

Kafa's daughters play with cats at her parents' home in Sanaa.

"Food prices have soared by up to 200 percent and the cost of living has increased by at least a third, so many daughters have been given away by families who wouldn't have dreamed of doing that before," Nadine Drummond, a spokesperson for Save the Children in Yemen, told CNN.

Both are easily preventable conditions brought on by the war.

According to the United Nations, more than 5,500 civilians have been killed in Yemen since March 2015, when a coalition led by Saudi Arabia launched a military campaign against Iranian-backed Houthi rebels in the country.

Because of restrictions on the borders, which have been shut completely at times, aid and fuel are scarce. Some 11.3 million people are in acute need of humanitarian assistance, and 8.4 million are just "a step away" from famine, according to the United Nations. UN Emergency Relief Coordinator Mark Lowcock warned in November that Yemen "will be the largest famine the world has seen for many decades."

All of these factors have intensified the problem of child marriages, which have long been a scourge in Yemen -- one of a handful of countries in the region without a legal minimum age of marriage. With a civil war raging, and almost no functioning government, it is unlikely that anything legally will change for Yemen's child brides any time soon.

Kafa bakes traditional Yemeni malawah bread.

And children are getting married younger. About 44% of girls are now married off before their 15th birthday, according to a survey conducted by UNICEF . The trend is on the rise, with girls as young as nine getting married, Meritxell Relano, UNICEF's resident representative in Yemen, told CNN.

"There are no jobs in the country. There is no agriculture. The system, the health system and the education system are collapsed or about to collapse," Relano said.

Three years into the war, families that have plunged into poverty and food insecurity are now resorting to desperate measures to survive.

"Unfortunately, many Yemenis see early marriage as a virtue. And war has made it worse," Ahmed Al-Qureshi, a Yemeni child rights activist, said.

Abdullah told CNN that he was aware of his daughters' dreams and aspirations -- but has no choice.

"There is a war and rockets are flying over our heads, homes are collapsing, our home shakes every time there is an airstrike, so what can I do?"

"I have no option but to marry my daughters early."

During her visit, Kafa takes over baking the main meal -- Yemeni malawah bread -- while her children play with a cluster of cats roaming the kitchen. Plastic containers are piled in a corner, ready for the daily trips the family makes to get potable water. Metal scraps and junk line the dirty brick courtyard at the heart of the family's two-room home. Halima shares one of those rooms with nine of her siblings.

Girls play in the courtyard of Halima's school.

Kafa wants a different destiny for her four daughters, and for her younger sister: an education, a chance at a better future, a choice.

"They will get married when they want, not when I want... I will never marry them off at a young age," she said.

But as the war rages on, their chance of pursuing an education looks bleak.

An estimated 2 million children are out of school in Yemen, where persistent bombardment has left 1,600 schools partially or completely damaged.

Teachers started this academic year with a strike to protest their unpaid wages. They are the only thing propping up the country's education system, which is on the verge of collapse.

"What could aggravate the problem even more is the complete halt of the education process in Yemen's most populous areas, which will lead boys to go to battle as child soldiers and girls to early marriages," Al-Qureshi told CNN.

Halima's school is still open, but many of her peers have stopped going.

On a recent afternoon, the remaining girls in her class could be seen playing in a sunny square outside her school. Dressed in their school uniforms, they stood in a circle dancing.

Halima leaves school with her mother.

"We don't want to get married, we want to finish our studies," Halima said.

"Girls like me that got married at a young age are now giving birth to their kids ... All these girls that are 11, 12, 13, they're so young."

"Their future is not good. We could grow old and become teachers or doctors and then get married. We thought when we get older, 22 or 25, then we'd get married, not when we're young. It doesn't work like this to marry off kids," she added.

When her parents picked her up from school, Halima, with her pink backpack slung over her shoulder, was all smiles. Her father took her by the hand and walked with her back home, chatting about her day, joking and laughing.

Despite everything, Halima is still optimistic.

"I crave having a good future, not (to) end up with the future of these other girls. I don't want to get married."

— CNN's Salma Abdelaziz and Eliza Mackintosh contributed to this report.