Thanks to alleged Iraqi tactics, the weather and the general blur of war, it has sometimes been difficult to tell Iraqi civilians from Iraqi fighters, and even to know whether the target in the crosshairs is a foe or a friend.
The Pentagon claims Iraqi fighters have shed uniforms for civilian dress and ditched their tanks for taxis. U.S. Marines fighting in An-Nasariyah over the weekend say some Iraqis pretended to surrender then shot at Marines who had passed them.
"With each passing day and every day an increasingly desperate Iraqi regime violates many international laws and all norms of human decency," Pentagon spokeswoman Torie Clark said Wednesday.
Iraqi regular army units are now traveling with women and children, Marines report. And some Iraqi soldiers are being forced to the front lines, the U.S. claims.
"Regime forces are seizing children from their homes and telling the males they must fight for the regime or they will all face execution," Brig. Gen. Vincent Brooks, a Central Command spokesperson, told a Thursday briefing.
In one town north of an-Nasariyah on Thursday, Marines were greeted with thumbs-up and smiles from Iraqi civilians — and then shots from snipers. They returned fire, and escaped any casualties, reports CBS News Correspondent John Roberts.
Chopper pilots of the 3rd Marine Aircraft Wing of the 1st Marine Expeditionary Force say they are growing wary of seemingly friendly crowds, where people wave their hands or white flags and then grab guns and fire potshots as the helicopters pass by.
"They'll do everything — wave at you, show their white shirts," said Maj. Stephen Hall. "As soon as you fly over them, they start shooting at us." After one such incident he found an armor-piercing bullet lodged in the floor just under his left foot.
"Before we started," said Maj. Chris Charleville, 34, of Cincinnati, "all the talk was that once we crossed into Iraq they would surrender in the thousands; civilians would welcome us with little flags. What we forgot was that no matter what people think of Saddam, no one likes to have their homeland invaded."
Night flying in Iraq is usually done without lights, and everything seems a threat. On more than one occasion, American helicopters have trained their guns on American vehicles on the ground, but have not fired.
The problem of identifying the enemy poses many problems.
If U.S. troops mistakes enemies for friends, they put their lives at risk. But mistaking civilians for combatants could lead not only to the tragedy of civilian deaths, but the political problems associated with them.
The Pentagon has stressed the effort of the coalition to avoid civilian deaths through the use of precision weapons.
The confusion in the field could also lead to the nightmare of killing fellow troops by friendly fire.
There already have been several reports of friendly fire incidents, including a British Tornado jet downed by a U.S. Patriot anti-missile battery. Two pilots died.
Several casualties were reported in a possible fratricide episode on an-Nasariyah.
Troops also complain that the enemy cannot even be trusted to follow common sense, if not the rules of war.
In clashes between American soldiers and Iraqi forces outside Karbala, southwest of Baghdad, Iraqi armored personnel carriers approached American positions but were hit by U.S. warplanes before getting within 10 miles.
"I can't believe they keep doing this. It's suicide to come at us like this," said Lt. Eric Hooper of Albany, Ga.
Iraqis have also used pick-up trucks to attack fully Marine units.
The uncertainty has made some troops jumpy. During an alert at a helicopter base, with word that Iraqis were approaching, Sgt. Nick Savena, 26, of Pittsburgh, thought he saw a tank advancing through the blowing sand.
"Three o'clock! It's right there in front of us!"
"Are you sure it's not a bush?" asked another.
" ... It's a bush, sir," came the shamefaced reply.