"We hadn't delivered a knockout blow. Milosevic was basically holding his own and despite these airstrikes we had not accomplished very much," Clark tells CBS News National Security Correspondent David Martin in an exclusive report.
NATO Secretary General Javier Solana was even more dissatisfied.
"He said 'this is bad news, this is not good,'" recalls Clark. "And as we talked about it, I realized of course what he was looking for was that with the onslaught Milosevic would just lay back, cover up and say, 'God, no! We're not going to resist this thing. Just call it off. Just call it off.'"
But the Serbs suffered so little damage just the opposite was in danger of happening. Clark got a call from Washington, from an official he refuses to name, saying it was the Clinton administration, not Milosevic, that wanted to call it off.
Now retired, Clark has written a behind-the-scenes book about NATO's air war which reveals a reality very different from the carefully scripted press briefings.
One reason Milosevic was able to hold his own: He had a copy of NATO's war plan.
"They had key portions of that operations order," says Clark. "It was given to Serb personnel by a traitor in the ranks at NATO headquarters.
Another reason: Clark was having trouble getting approval to strike the targets he wanted.
"We always were fighting the problem of how many targets can we get approved," he says.
Target lists had to go all the way up the chain of command to the Oval Office. Clark says it was the president who was giving the final approval.
For Clark, who as a junior officer had come home from Vietnam on a stretcher, it was an echo of President Lyndon Johnson picking politically correct, but militarily ineffecive targets in North Vietnam.
"We weren't going to make that mistake in this campaign," says Clark.
But it seemed the same mistake was being made and no one wanted to admit it. When Clark told reporters after one month of bombing that Milosevic had not stopped the ethnic cleansing in Kosovo and was actually sending in reinforcements, he got a phone call from Gen. Hugh Shelton, Chairman of the Joint Chiefs of Staff.
The inability to stop the ethnic cleansing was perhaps the biggest failure of the bombing campaign. Clark wanted to use Apache helicopters to attack the Serb forces committing the atrocities.
Check back Tuesday for more on other battles Clark fought and lost not with the Serbs, but with the Pentagon.
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