Israel's army is changing. Once proudly secular, its combat units are now filling with those who believe Israel's wars are "God's wars".

Military rabbis are becoming more powerful. Trained in warfare as well as religion, new army regulations mean they are now part of a military elite.

They graduate from officer's school and operate closely with military commanders. One of their main duties is to boost soldiers' morale and drive, even on the front line.

This has caused quite some controversy in Israel. Should military motivation come from men of God, or from a belief in the state of Israel and keeping it safe?

The military rabbis rose to prominence during Israel's invasion of Gaza earlier this year.

Some of their activities raised troubling questions about political-religious influence in the military.

Gal Einav, a non-religious soldier, said there was wall-to-wall religious rhetoric in the base, the barracks and on the battlefield.

As soon as soldiers signed for their rifles, he said, they were given a book of psalms.

And, as his company headed into Gaza, he told me, they were flanked by a civilian rabbi on one side and a military rabbi on the other.

"It felt like a religious war, like a crusade. It disturbed me. Religion and the army should be completely separate," he said.

'Sons of light'

But military rabbis, like Lieutenant Shmuel Kaufman, welcome the changes.

In previous wars rabbis had to stay far from the front, he says. In Gaza, they were ordered to accompany the fighters.

"Our job was to boost the fighting spirit of the soldiers. The eternal Jewish spirit from Bible times to the coming of the Messiah."

Before his unit went into Gaza, Rabbi Kaufman said their commander told him to blow the ram's horn: "Like (biblical) Joshua when he conquered the land of Israel. It makes the war holier."

Rabbis handed out hundreds of religious pamphlets during the Gaza war.

When this came to light, it caused huge controversy in Israel. Some leaflets called Israeli soldiers the "sons of light" and Palestinians the "sons of darkness".

Others compared the Palestinians to the Philistines, the bitter biblical enemy of the Jewish people.

Israel's military has distanced itself from the publications, but they carried the army's official stamp.

Still, army leaders insist their rabbis respect military ethics and put their private convictions aside. They say the same about the new wave of nationalist religious solders joining Israel's fighting forces.

'Religious duty'

I visited an orthodox Jewish seminary near Hebron in the West Bank. It is one of an increasing number of religious schools that encourage taking the Jewish Bible to the battlefield.

All students at the seminary choose to serve in Israel's combat units while statistics suggest less ideologically driven Israelis are avoiding them. This has made headline news in Israel.

The 19-year-olds I spoke to at the seminary told me religious soldiers like them can make the army behave better and become "more moral".

They believe it is their religious duty to protect the citizens of Israel, the Jewish state. The Lord commands it, they said.

The students' seminary is built in a Jewish settlement in the occupied West Bank.

If President Barack Obama gets his way, Israel will eventually evacuate most settlements.

They are illegal under international law and Palestinians claim the territory as part of their future state. But for the religious soldiers the West Bank is part of land given to the Jews by God.

Gal Einav thinks many soldiers will refuse to close settlements down.

The settlement issue could well tear the army apart, he told me, adding that most of his officers were settlers these days.

"If it comes to a clash between political orders from Israel's government and a contradictory message from the rabbis, settlers and religious right-wing soldiers will follow the rabbis," he said.

Threat of 'Jihad'

Israel's military leaders strongly disagree.

Brig Gen Eli Shermeister is the army's chief education officer.

He admits some mistakes were made in the past but says the right balance has now been found with the military rabbis.

He insists Israel's military commanders are the only ones in charge of the soldiers' spirit.

"The moral code of Israel's army is clear. We judge soldiers in the light of this code. Nobody can create another moral code. [Certainly] not a religious one."

But Brig Gen Shermeister's predecessor describes what he sees as clear and worrying changes within the military.

According to Reserve Gen Nehemia Dagan, what is happening in the army is far more dangerous than most Israelis realise: "We (soldiers) used to be able to put aside our own ideas in order to do what we had to do. It didn't matter if we were religious or from a kibbutz. But that's not the case anymore.

"The morals of the battlefield cannot come from a religious authority. Once it does, it's Jihad. I know people will not like that word but that's what it is, Holy War. And once it's Holy War there are no limits."

Many religious Jews object to the type of preaching heard during Israel's recent Gaza operation.

They say it perverts the true teachings of Judaism as well as contradicts Israel's military code.

Day to day, Israel's army mainly operates in civilian areas - in Gaza, the West Bank and in East Jerusalem.

The influences that Israeli soldiers are exposed to are extremely significant.

How they view the Palestinians who live here is likely to affect the way they use their power and their weapons