NAGO, Okinawa -- On April 25, workers began dumping stone into the cobalt blue waters just off the shore in this city's Henoko district, launching construction of a U.S. Marine Corps' runway while also sparking unprecedented anger and sadness across Japan's southernmost prefecture.

The stone is for a breakwater, the first major step in land reclamation for the new runway being built by the Japanese government at the U.S. Marines' Camp Schwab. The runway and other new facilities will replace U.S. Marine Corps Air Station Futenma in Ginowan, Okinawa Prefecture, which the United States agreed to close and return to Japan some 21 years ago.

In that time, Okinawans and other supporters voted and protested countless times against Futenma's relocation within the prefecture. And many of them were at Henoko on April 25, raising their fists and shouting their opposition from outside Camp Schwab and from small craft just offshore.

More than 10 Japan Coast Guard (JCG) boats were already stationed at the water's edge early in the morning, on high alert for the approach of seaborne anti-base protesters. At about 9:20 a.m., the first 3-meter by 3-meter bag of stone was dropped into the blue water by a crane on the beach. A prefectural official watched through a pair of binoculars from atop a lookout point about 2 kilometers away, and hurriedly made a call to Okinawa prefectural headquarters.

More than 10 boats and canoes carrying protesters soon approached, getting as far as the floating fence around the site set up by the government to keep them out. JCG rubber boats and other craft swept in to confront the protesters in an apparent attempt to block their progress.

At about the same time, about 100 locals gathered outside Camp Schwab's front gate, holding placards with slogans including, "Stop the Henoko reclamation" and chanting, "Stop the construction!"

"Mainland Japanese people say that U.S. military bases are necessary, but they never offer to take on some of the burden of hosting them," Makoto Yasu, a 51-year-old man from the Okinawa town of Yonabaru who has participated in sit-ins at the gate for some three years, told the Mainichi Shimbun. The start of reclamation work "is a ceremony to force the Okinawan people to give up."

Regarding Okinawa Gov. Takeshi Onaga, who has made several attempts to halt the base construction and was even sued by the central government, Yasu said, "Basically, I want him to make good on his promise not to let them build a base at Henoko."

Mayumi Shiroma, a 38-year-old protester from the village of Yomitan, told the Mainichi, "The (land reclamation) work comes as a shock. They are doing something to the ocean that can never be undone." She added, "If we give up, it's all over. I've done everything I can about this as a mother living on this island. I want to change Japan starting right here in Okinawa."

However, some locals have accepted the new base, though with mixed feelings.

"I was raised with the sea, so it's tough seeing the work go ahead," said 67-year-old Masayoshi Kyoda, who has run the local supermarket for about 20 years. Just after the end of World War II, the people of Henoko staved off starvation by getting food from the sea. There was a time when he opposed the new base, but eventually accepted it.

"The government wouldn't listen no matter how loudly we protested," Kyoda lamented. "The base was inevitable."