I had then set up a committee of top men and had asked them to study with great care the implications the new weapons might have for us. It was their recommendation that the bomb be used against the enemy as soon as it could be done. They recommended that it should be used without specific warning and against a target that would clearly show its devastating strength. I had realized, of course, that an atomic bomb explosion would inflict damage and casualties beyond imagination. On the other hand, the scientific advisers of the committee reported, "We can propose no technical demonstration likely to bring an end to the war; we see no acceptable alternative to direct military use." It was their conclusion that no technical demonstration they might propose, such as over a deserted island, would be likely to bring the war to an end. It had to be used against an enemy target.

using this context write me a 3 sentence main idea

The main idea of this passage is that the writer, after setting up a committee to study the implications of new weapons, received a recommendation to use the atomic bomb as soon as possible. The committee concluded that no technical demonstration would effectively end the war, and therefore, it was necessary to use the bomb against an enemy target without specific warning to demonstrate its devastating strength. Thus, the main idea is the justification for the decision to use the atomic bomb.