Relentless Pressure

The war, like a seesaw, took two interlocking directions at once last week. American planes took advantage of the last clear days before the monsoon to wreak unusually heavy damage on North Viet Nam. To the south, the enemy shied away from major actions and, bowing to the superiority of U.S. firepower along the Demilitarized Zone, broke off the lengthy siege of the Marine base at Con Thien. Though Con Thien is not yet home free, its relief was a psychological boost to the entire U.S. effort in Viet Nam.

The South. For the past six weeks, in one of the greatest artillery duels in history, North Vietnamese army gunners have rained as many as 900 rounds of big artillery and mortar shells a day on the Marine stronghold two miles south of the DMZ. Last week, as they poked their heads out of their muddy dugouts, the Marines at Con Thien noticed an unusual absence of the harsh hiss of incoming shells. U.S. aerial reconnaissance found out why: in groups of 10 and 15, North Vietnamese regulars were spotted making their way northward out of the DMZ, leaving behind some abandoned gun emplacements. Plagued by problems of supply and outgunned by the U.S. response, which daily included at least 5,000 artillery shells and 1,000 tons of bombs dropped from B-52s, the North Vietnamese, at least for the moment, drastically reduced their barrage. Perhaps moving to higher ground to escape monsoon flooding of their emplacements, they lobbed only 40 or 50 rounds of shells a day on the Marines.

General William C. Westmoreland called Con Thien "a Dienbienphu in reverse," but he added that the Reds would probably be back. Even so, Con Thien represented a U.S. victory. The Marines had taken the best that the Communists could throw at them and had held their ground and fought back valiantly and effectively. Their showing can only have given some pause to Hanoi's war strategists.

The North. In their pre-monsoon onslaught, U.S. flyers hammered relentlessly at North Viet Nam's lines of communication, over which its war supplies are funneled from China and the port of Haiphong to the south. Returning to the normally proscribed 20-mile-wide buffer zone along the Chinese border, U.S. airmen scored direct hits on the previously damaged Lang Son bridge, the major rail link between Hanoi and China. Venturing within one minute's flying time of the Chinese border, U.S. raiders knocked out three previously untouched highway bridges over which the North Vietnamese had been trucking supplies in an effort to offset the rail delays.

U.S. airmen continued the strategy of trying to cut all rail and road access to the port of Haiphong so that incoming supplies will not reach the war zone. For the third time in a month, they bombed a highway bridge only eight-tenths of a mile from Haiphong's heart, this time dropped the center span. Scratching another target from the dwindling list of forbidden objectives, they hit a fuel dump at Tien Nong, seven miles northwest of Haiphong. The storage tanks were believed to hold 700 tons of oil for North Vietnamese trucks and power stations. The estimate was probably right: smoke from the fire rose more than two miles into the sky.

How effective is the U.S.'s monthold choke-and-destroy bombing strategy? U.S. air experts pointed to the silent cannon facing Con Thien as one example. The artillery shells that the Communists had been firing at the Marines weigh about 21 Ibs. to 107 Ibs. apiece. If the trains do not run and the trucks cannot pass, shells of that size simply do not find their way south in sufficient numbers to enable the North Vietnamese gunners to match muscle with U.S. Marines.

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