PARIS - The Nazis thought the jagged cliffs were unassailable until the elite U.S. Rangers scaled them in a valiant D-Day assault. Now the rocks are undergoing major surgery to save them from an even greater force - Mother Nature.

The cliffs at Pointe du Hoc, the Normandy promontory where the Rangers stared down death, have eroded by 33 feet since June 6, 1944. Today, the job is to strengthen the cliffs, not conquer them, and keep the bunker used by the Nazis as an observation point from falling into the pounding sea.

"If we leave it this way, the cliffs will crumble all by themselves," said Philippe Berthod, director of the Pointe du Hoc operation for GTS, a Lyon-based company that specializes in delicate operations, often on sites with difficult access.

But fixing the cliffs, made of limestone mixed with clay, is just buying time - 50 years is an optimistic estimate, Berthod said. Harsh winters and a raging storm can play havoc, he said. "Our work is to slow the erosion phenomenon."

Just like the U.S. Army Rangers, some of the 20 GTS workers are scaling the cliffs on ropes. But they're also using a crane, ton upon ton of cement to fill up gaping holes and metal bars measuring up to 26 feet to nail the sides of the cliff in place. Up top, they are putting what amounts to a safety belt around the once formidable Nazi bunker.

Some 500,000 people visit the Pointe du Hoc each year, although the bunker has been closed to the public since 2004.

"This is saving an important part of our public memory," said James Woolsey of the American Battle Monuments Commission, which ordered the $6 million job that started in February and is expected to be finished in October.

The Pointe du Hoc assault to prepare the way for American troops stands out as a particularly valiant D-Day moment.

The U.S. Army's 2nd Ranger Battalion went in with the 5th Battalion to climb the 120-foot spikes of limestone four miles west of Omaha Beach to put out of action six 155mm Nazi howitzers. The weapons were capable of firing from concrete bunkers down on the landing sites at Utah and Omaha, two of the five beaches stormed by U.S. and British troops to break Hitler's stranglehold in western France.

Of the 235 men who took on the cliffs, only 90 were fit for battle two days later. The rest were dead or wounded but, reads the Rangers Creed, "Surrender is not a Ranger word."

The observation bunker at the promontory on Pointe du Hoc "was the eyes of the entire German operation," said Woolsey.

"The bunker is actually in very good shape," said Woolsey. But "we knew if something was not done soon, the Pointe would fall off the cliff."

To secure the bunker, cement beams linked to 18 stakes to be driven 79 feet into the ground will act as a safety belt for the vulnerable east and west facades.