TENSIONS MOUNT between the U.S. Navy, which desires to continue practice bombing on Vieques, and virtually the whole population of Puerto Rico, Vieques's mother island. Navy gunfire on the island accidentally took a civilian life last spring, transforming a long-smoldering resentment of Navy autonomy into full-fledged outrage over Puerto Rico's still-colonial dependency.

The Navy's latest gambit is to prepare to send in a carrier battle group for the live-fire training the Navy insists is essential to prepare the group for an early Persian Gulf/Mediterranean patrol. Will the commander in chief feel up to conducting this training in the face of the massive Puerto Rican protests now being planned if the Navy resumes training fire? Would he face down the criticism he could expect to draw at home if he restricted the training? To head off a crisis, Washington badly needs to absorb recent turns in the Vieques debate.

A sworn statement by retired Vice Adm. John J. Shanahan--a consultant to the government of Puerto Rico--all but collapsed the Navy's insistence that Vieques offers a critical and unique place for practicing amphibious landings. The Marine Corps doesn't do opposed amphibious landings anymore, hasn't since Inchon in Korea, the admiral said. He wasn't merely challenging the rationale for pounding Vieques. He was undermining the core mission the modern Marine Corps still is substantially built for.

Add a telling point made by Puerto Rico's governor, Pedro Rossello. On Vieques there is an inner range, on the island, where weapons explode, and an outer range, at sea, where weapons sink in the sea. Let training continue on the outer range, the governor argues, but halt live-fire training on the inner range--on the island, on part of which 9,000 American citizens live. Thus could the Navy retain useful training grounds and give Vieques residents security on their home island.

Of course Vieques is a symptom of the larger long-neglected political crisis arising from Puerto Ricans' lack of the full rights that other Americans enjoy. Perhaps one key to the larger question lies in Vieques.