Her face covered in mud, 18-year-old Smadar crawls beneath thorny brush, her automatic rifle around her neck.

She smiles despite the intensity of the training, and her commander, also a woman, shouts encouragement.

"I don't regret choosing this unit," said Smadar, who was not allowed to provide her last name under Israeli army rules.

"I wanted to do my military service in the most combative unit possible."

Smadar is part of a discreet but profound change taking place within the Israeli military, with a growing number of women taking part in combat units.

Just four years ago, some three percent of enlisted women served in combat units compared to seven percent today, according to the army.

That number is expected to rise even further to 9.5 percent in 2017.

The increase has come both due to changes in society, with women's participation in combat units no longer dismissed, and a shortage in available soldiers due to reductions in the amount of required service time for men.

Israel's military is an institution at the heart of society, with nearly all Jewish citizens required to serve, and such changes are likely to reverberate beyond the barracks.

- Equal right to serve -

Even before the state of Israel was created in 1948, women played an important role in the Haganah, the forerunner to the country's military, today the region's most powerful.

Currently men are required to serve two years and eight months after they turn 18, while women serve two years.

Women's roles had historically been confined to such positions as nurses or radio operators -- an arrangement undergoing rapid change.

The first mixed unit, known as the Caracal battalion, was formed in 2000, taking its name from a type of wild cat whose males and females look the same.

It was that year that the law was amended to state that "women's right to serve in any position is equal to the right of men."

Smadar, who was training in the hills of the Galilee in the country's north, is preparing to join the Bardelas battalion and will likely be stationed in the semi-desert south.

Bardelas is one of what are now three mixed combat units in the Israeli army. A fourth battalion is planned for March 2017.

Women wanting to take part in combat units must commit to serving eight more months, an equal amount of time as men. It has not dissuaded volunteers.

"What a man can do, a woman can also do," said Smadar.

A 25-year-old woman from the Caracal battalion wondered why all units cannot be mixed.

She arrived in Israel in 2004 from Ukraine and said she wanted to do whatever possible for her new country.

"Whoever can fight must do it," she said. "Man or woman -- there is no difference."

- A global trend -

Israel's experience is similar to trends globally, said Megan Bastick of the University of Edinburgh, who has studied women's participation in security forces.

"Across the Western world, there has been a general increase over recent decades in the proportion of women joining the military," she said.

She cited Australia and Canada as two countries in particular offering equal opportunities.

In the Middle East, fighter pilot Major Mariam al-Mansouri led a combat mission for the United Arab Emirates against Islamic State group jihadists in 2014, recalled Dalia Ghanem-Yazbeck of the Carnegie Middle East Centre.

Algeria has a number of women generals, while women also serve in Jordan, Lebanon and Tunisia, she said.

In Syria, a number of women hold the rank of general and fight in combat units.

Ghanem-Yazbeck says that remains the exception.

Within combat units in the region, women often "continue to be in traditional gendered positions such as translators or data-entry personnel or social workers and so on."

"Despite an evolution, women remain the aides of their male counterparts."

- Integration tool -

Israel's army has served as an integration tool for society, bringing in Israelis of different ethnic backgrounds as well as sexual orientations, a contrast with the conservatism of much of the region.

The military is thought to include more than 120,000 soldiers in mandatory service -- an estimation since the army does not provide such figures.

More than 41 percent of those serving are women, the military says, and 85 percent of army posts are available to women.

More than half of women serve, with ultra-Orthodox Jewish families exempt.

Amos Harel, defence correspondent for influential Israeli newspaper Haaretz, said the increase in women does not reflect "ideology but a need," with the timeframe for men to serve recently reduced from 36 to 32 months.

Mixed units operate along relatively calm borders, including those with Egypt and Jordan, the only two Arab countries with peace treaties with Israel.

Other units are assigned to more risky areas, such as the Lebanese border and along the Gaza Strip.

Forty-four female soldiers have been killed in combat since 1948.

Harel questions whether the military will follow through and allow women to serve in all roles at the risk of what has concerned many: one of them being kidnapped.

The kidnapping of male soldier Gilad Shalit in 2006 by Hamas caused shock nationwide.

"One cannot help wonder whether the response to the abduction of a female soldier would be more extreme," Harel wrote recently in Haaretz.