No one ever claimed there wasn't a 'general time horizon' for withdrawing troops. The problem was in setting numbers and dates. In fact, they've slowly been reducing the numbers since the surge began having successes.

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"We are fighting today for our life, for our liberty, for our all, we cannot go on being led as we are. Somehow or other, we must get into the Government men who can match our enemies in fighting spirit, in daring, in resolution and in thirst for victory."~Leo Amery 1940, while staring at Chamberlain