Yariv Oppenheimer attends a demonstration calling for the removal of West Bank settlements outside the unauthorized settler outpost of Migron on Jan. 7, 2008, in the West Bank. (David Silverman/Getty Images)

JERUSALEM – He’s usually at the forefront in the battle against Jewish settlements in the occupied West Bank. But in a weird twist of fate, activist Yariv Oppenheimer has spent the past week defending one of those controversial developments — as part of his military reserve duty in the Israeli army.

“Even though I don’t always agree with government policy, I am doing this because I believe it is my civic duty in a democratic country," Oppenheimer, general director of Peace Now, an Israeli organization that opposes all settlement construction in the Palestinian territories and regularly petitions Israel’s courts against such building, said in an interview.

“I want to believe that when the day comes that the order is not to guard settlements, but to vacate settlements, then my friends on the right would"  also comply, he wrote on his Facebook page.

Oppenhemier is fulfilling his military duty — a yearly obligation required of all Israeli men until at least age 40 — in Mevo Dotan, a settlement in the northern tip of the West Bank. He has two remaining weeks of service.

More than 120 official settlements big and small are scattered throughout the West Bank and in annexed East Jerusalem. Together, they are home to as many as 500,000 Israelis, according to Israel's Central Bureau of Statistics.

The settlements are a constant source of tension because they sit on lands Palestinians hope to use one day for an independent state. Most of the world's governments consider them violations of international law. The White House has condemned settlement construction, called it "illegitimate," and said the communities pose a serious obstacle to peace efforts between Israelis and Palestinians.

Oppenheimer, for his part, said that guarding a settlement was giving him the opportunity to see the situation up close and from a different perspective. Settlements, many of which sit close to Palestinian areas and have been the targets of bloody terror attacks, have strict security arrangements. Army and civilian guards man the entrances and do regular patrols.

“I am seeing the reality of Israel’s occupation,” said Oppenheimer, who usually approaches the settlers as a political antagonist. He said the experience is “not changing my views but actually strengthening them.”

Peace Now is known for its damning reports on the expansion of Israeli settlements and illegal outposts. Oppenheimer, a familiar figure to many Palestinians and Jewish settlers, said he realized Palestinians might be offended by seeing him wearing an Israeli army uniform and patrolling a settlement. But, he said, “they need to understand that I am an Israeli citizen and I must respect the law.”

“Some of Israel’s strongest leaders, who made the biggest concessions towards peace, were also soldiers,” he said, acknowledging that some Israelis refuse to serve in the army for ideological reasons.

Oppenheimer said the settlers have received him warmly.

“They knew I was coming and were waiting for me. They wanted to talk to me,” he said. “They thought it was a unique chance to meet with a left-wing person and to talk to me without the media around.”

Settler leader Gershom Mesika, who heads the regional council of settlements in the northern West Bank, laughed when asked about the irony of Oppenheimer guarding one of the settlements he regularly criticizes.

“I welcome him. I hope that he enjoyed the view, the people and the community spirit we have here,” he said in an interview. “He might even consider moving here now.”

Mesika noted that his council had already given Oppenheimer the tongue-in-cheek title of  "honorary citizen” in Samaria — the biblical name used by settlers for the northern portion of the West Bank — following a 2012 court petition filed by Peace Now against what it alleged was unlawful settlement construction. The petition instead led to Israel approving more construction.

“We welcome him here and hope he would even consider building a home here after he finishes his reserve duty,” Mesika said.