The memo was finished one day after President Bush interviewed Robert M. Gates, the president of Texas A&M University, as a potential successor to Mr. Rumsfeld and one day before the midterm elections. By then it was clear that the Republicans appeared likely to suffer a setback at the polls and that the administration was poised to begin reconsidering its Iraq strategy.

The memo provides no indication that Mr. Rumsfeld intended to leave his Pentagon post. It is unclear whether he knew at that point that he was about to be replaced, though the White House has said that Mr. Bush and Mr. Rumsfeld had a number of conversations on the matter.

Told that The New York Times had obtained a copy of it, a Pentagon spokesman, Eric Ruff, confirmed its authenticity. “As it became clear that people were considering options for the way forward, the secretary had some views on the subject, and this memo reflects those views,” he said.

At the Pentagon, Mr. Rumsfeld has been famous for his “snowflakes” — memos that drift down to the bureaucracy from on high and that are used to ask questions, stimulate debate and shape policy. Mr. Rumsfeld’s Nov. 6 memorandum, circulated as part of the administration’s review of Iraq policy, is written in that spirit and with the same blunt aphorisms that Mr. Rumsfeld frequently uses in public.

Unlike the lawyerly memo on Iraq policy submitted Nov. 8 by Stephen J. Hadley, the national security adviser, Mr. Rumsfeld’s listed more than a dozen “illustrative options” that the defense secretary did not endorse, but suggested merited serious consideration. “Many of these options could, and in a number of cases, should be done in combination with others,” Mr. Rumsfeld advised.

With Mr. Rumsfeld’s resignation, the options no longer have the same weight. In recent weeks, some have been discarded as the Bush administration tries to adjust its military and political strategy in Iraq. But others, like increasing the number of advisers attached to Iraqi forces, live on and have also been recommended by others.

Mr. Rumsfeld, who has presided over two wars and is one of the longest-serving Pentagon chiefs, is scheduled to leave when his designated successor, Mr. Gates, is confirmed by the Senate, expected later this month.