Israeli tank units and ground troops are now massing along the border with Gaza, one week after the Hamas attacks.

Some experts believe the expected invasion by Israeli Defense Forces could be imminent.

“The expectation is that it will be a combined assault,” said Eric Schwartz, a former U.S. assistant secretary of state, now a public affairs professor at the University of Minnesota. “Air assets as well as a significant number of troops going in and conducting urban warfare.”

“Approximately 4% of Israel’s population is in uniform right now,” added Ethan Roberts, the deputy executive director of the Jewish Community Relations Council of Minnesota and the Dakotas. “So, we’re talking over 300,000 men and women. It is a massive mobilization of reservists.”

Israeli Special Forces troops have been carrying out raids inside Gaza — searching for hostages, Hamas weapons and defenses.

Israeli warplanes are bombarding the area with air strikes in retaliation for the killing of 1,300 Israelis and the kidnapping of dozens of others by Hamas terrorists.

“We saw bodies,” said Lieutenant Colonel Richard Hecht, an Israel Defense Forces spokesperson. “We saw the massacre. We saw the ISIS-style carnage.”

The Israeli government has been leafletting Gaza, calling for more than 1 million civilians to evacuate to the south.

“The camouflage of the terrorists is the civil population,” Israeli Defense Minister Yoav Gallant told reporters. “Therefore, we need to separate them. So those who want to save their life, please go south.”

Thousands of Palestinians are fleeing from the north by car, donkey-drawn wagons, or by walking.

Some are carrying just a few possessions, fearing they may never be able to return home.

“Everything that I have. We’re leaving our house right now and we don’t know where to go,” said Tala Herzallah, 21, who said there were bombings as they tried to evacuate. “Please, please, try to let everyone know how much we are suffering, how much we are dying. We have to move; the world has to move.”

The United Nations is calling is calling for a reversal of the evacuation order.

“Moving more than 1 million people across a densely populated war zone is extremely dangerous, and in some cases, simply not possible,” said U.N. Secretary-General Antonio Guterres.

ABC News reports the death toll in Gaza is at 2,200 and rising.

The U.N. is calling for Israel to not target civilians, hospitals, schools, clinics and U.N. locations.

“To ensure there aren’t civilian deaths is nearly impossible,” Schwartz said. “But there are rules of war that require that you seek to minimize civilian casualties in warfare, and certainly in a campaign like this.”

The Israeli offensive is expected to target Gaza City, in the north.

“That is where Hamas has embedded itself, within the civilian communities,” Roberts noted. “That is where Hamas used civilian communities as cover, to launch rockets at Israel.”  

He says both Israeli and Palestinian civilians are suffering.

“Hamas as a terrorist organization is trying to strike terror in the hearts of Israeli citizens,” Roberts said. “On the flip side, in Gaza, civilians are how Hamas tries to maintain their military power by literally embedding themselves in civilian neighborhoods, hiding their weapons in mosques and hospitals, using ambulances to move weapons back and forth.”

A State Department spokesperson says 29 Americans have been confirmed dead in Israel, and 15 U.S. citizens and one lawful permanent resident of the U.S. are still unaccounted for.

The Associated Press reports there are an estimated 500 Americans in Gaza.

The State Department says it’s working around the clock to determine their whereabouts and advise the U.S. Government on hostage recovery efforts.

Roberts doesn’t mince words about what he thinks will happen when Israel launches its invasion of Gaza.

“It’s going to be awful for everyone,” he said. “There’s going to be a lot of people dying, a lot of civilians dying, and a lot of Hamas terrorists dying.”