"It's clearly a combination of both. Show me a link where a reputable military leader is saying the surge is not at least partially responsible for bringing down the violence."

Surge is useful in terms of adding confidence, and particularly in regards to a commitment that we aren't leaving. But a change in tactics and build up in knowledge of Iraq in general, is the most significant aspect.

"It is absolutely transparent that you are making a feeble attempt to defend Bush and Rumsfeld for their arrogant refusal to listen to the Generals asking for more troops."

This war has always been about whether we as a nation have the will to outlast [in terms of time] the terrorists.
If you wanted twice the army size in Iraq, then the costs of the war would be twice as much as it was. And at least 50% more US causalities [though probably significant less Iraqi troop causalities- maybe 1/2 as much- which a lot of Iraqi soldiers deaths.]
To put numbers in, current US deaths are 3860, so instead it would be over 5000. Current Iraq soldier deaths is 7630 so instead it probably have been less than 5000.
http://www.icasualties.org/oif/IraqiDeaths.aspx
http://www.icasualties.org/oif/

So part of this war is determining the possible long term support of it. Considering how little support there was by the Dems [and their keen desire to relive Vietnam] and the amount of wacked out opposition they fomented, it seems if anything we should have used less US troops.