What is the U.S. doing to deter China from attacking Taiwan?

Tokyo — President Biden was on his way home Tuesday from his first trip to Asia as the American leader. His last day included a summit with the three other leaders of the so-called Quad alliance: India, Japan and Australia.

“The United States must and will be a strong, steady, enduring partner in the Indo-Pacific,” Mr. Biden vowed as he stood next to Japanese Prime Minister Fumio Kishida, India’s Narendra Modi and Australia’s freshly elected leader Anthony Albanese. All share America’s concern with an expansionist and aggressive China.

On Monday President Biden said the U.S. would intervene militarily to defend Taiwan from its massive neighbor.

CBS News senior foreign correspondent Elizabeth Palmer has been to visit some to the U.S. troops who could end up on the front line in any Indo-Pacific conflict.

Some 50,000 U.S. troops are based in Japan alone — more than in any other country outside the U.S.

Palmer joined the Third Battalion, 2nd Marines as they carried out a training exercise in the pouring rain on the island of Okinawa.

Lieutenant Robert Booker and his platoon were defending a patch of turf against a theoretical enemy, but there wasn’t a Marine taking part that didn’t know the exercise was a rehearsal for a possible Chinese invasion of Taiwan.

“Especially looking at the terrain,” Booker told Palmer. “This is what we would encounter there.”

The island of Taiwan considers itself independent. China insists that it is not, and has vowed one way or another to repatriate the territory.

On Monday, President Biden said the U.S. would intervene if China moved to seize Taiwan by force.

He said it wasn’t a change in policy, and the White House also put out a statement stressing that its position had not changed from the long-espoused “strategic ambiguity” — that is, keep the Chinese guessing what a U.S. response would actually look like.

China regularly sends military planes and ships on muscle-flexing sorties around Taiwan. Beijing calls America’s military presence in the region a provocation.

So far, it has remained a war of words. That, said Palmer, is where The Quad comes in.

The U.S. has staged joint military exercises with Japan, India and Australia in the Indo-Pacific, signaling that if push should ever come to shove, America will not stand alone.