The disaster in Iraq should have taught us that military intervention cannot hasten democracy.
For one thing, this seems an overgeneralisation from one example. West Germany post-1945 springs rather quickly to mind.
But more than that, one may agree that the Iraq war caused a disastrous loss of life and was utterly wrong while still doubting that the country would have made faster progress towards democracy if there had been no war.
War does not in itself bring democracy, but can – in some circumstances – remove obstacles to it.