Trouble in South China Sea

A tense, hours-long standoff between China and the Philippines unfolded on August 5 near Ren'ai Jiao, a reef in the South China Sea. The China Coast Guard blocked two Philippine navy vessels from intruding into the adjacent waters of Ren'ai Jiao. The Philippine ships were delivering construction materials to a broken military vessel that has been grounded on the reef since 1999. The standoff sparked immediate criticism from the Philippines and the U.S, which China promptly rejected. How did a rusty warship get grounded on the reef in the first place? What exactly happened during the standoff? And what’s the business of the United States in this matter?