It was reported at the time that President Johnson took an active role selecting bomb targets in Vietnam:
If the newspapers are to be believed he made the selection calls sitting on the toilet seat in the White House. Since almost all bombs were dropped over empty forest it’s hard to see why anybody would be concerned about which particular trees were killed.
There were of course suitable bomb targets in the North. Hanoi almost escaped bombing until the fall of ’72. It was not a major industrial city but nevertheless in World War II We blew up many harmless cities in Germany and Japan. I occasionally visit Wurzeburg, a pretty little city without industry. It was leveled late in the war for no known reason. Certainly Hanoi made at least an equally worthwhile bomb target.
There were two other a rather good bomb targets. The northern boundary of Vietnam is mountainous although not a major mountain range. There were two railroads connecting with China running through this mountain range. Breaking them up by use of fighter-bombers and then keeping them non-operational permanently was militarily obvious and probably worthwhile. Certainly far more worth while than Wurzeburg.
The North of Vietnam is very largely the lower reaches of the Delta of the Red River. This being on the outskirts of the traditional rice growing area of Asia it had been thoroughly converted into a long series of irrigated and drained rice paddies. Breaking up the dikes would have been an easy thing for the air force to do and it might have starved the North Vietnamese government out. We announced that we were not going to do that at the very beginning of the war.
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But let us now turn to various other things that were not done although the fact that they were not done was the open secret. The first of these is blockade of the North. There was no blockade until after the ‘72 election when Nixon imposed a blockade and ordered a bombing of Hanoi. This speedily changed the northern negotiating tactics in the attempt to make peace. Thus the open war ended at this time to be renewed later, of course. I never saw any explanation as to why the blockade had not been put on earlier.
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The North of Vietnam sent most supplies to the south by way of the Ho Chi Minh Trail which ran through Laos. This ran parallel to the Laotian South Vietnamese border and not terribly far from that border. We did not however make any serious effort to block it. It was bombed from time to time, but it was in the forest and only a trail anyway so this did not do very much in the way of blocking it. On one occasion the South Vietnamese army mounted a light raid on it but quickly withdrew. The only explanation I never heard for failing to make any serious effort to block the trail was a statement by a employee of the Department of State in Washington in which he said that if we moved into Laos the Vietnamese would simply move their trail westward into Thailand, thus bringing the Thais into the war. Why that was thought to be undesirable, was not explained. Surely if they were trying to defend their own territory against the North Vietnamese, their intervention in the war would’ve been to our advantage.
I might not be quoting this exactly, but when Curtis LeMay was asked why the U.S. Air Force could not subdue Vietnam despite being able to do so in Japan, Le May remarked, “In Japan I was doing the targeting. In Vietnam McNamara was.”