Another 40,000 US troops for Afghanistan?

If President Obama eventually agrees to support General Stanley McChrystal's recommendation of more US troops in Afghanistan, just how many troops is that likely to be? No-one outside the Pentagon knows for sure, as the figures are not contained in the General's report.
However, Frederick W. Kagan, director of the Critical Threats Project at the American Enterprise Institute and Kimberly Kagan, President of the Institute for the Study of War, have produced a report that offers some estimates.
A Comprehensive Strategy for Afghanistan: Afghanistan Force Requirements argues that an additional 40-45,000 troops will be necessary in 2010 to add to the 64,000 already there.
(It should be noted that, according to the authors, of the 64,000 troops presently in-country, only 23,000 are available for counter-insurgency operations.
Compare that to Iraq, where before the troop surge the 15 US brigades there could put around 72,000 counter-insurgency troops on the ground and at the height of the surge, the total was more like 105,000. Iraq and Afghanistan have similar populations, although the latter is a much bigger country.)
These troops are in addition to the 20 non-US ISAF battalions that provide another 16,000 counter-insurgency troops and around 50,000 Afghan National Army troops. It will also be necessary to speed up the training of an extra 30,000 Afghan troops by October next year.
The US and ISAF troops should concentrate their efforts in Helmand/Kandahar, Paktia/Paktika and Nangahar and the Konar River Valley, say the authors. Other areas should simply be held or, in some cases, abandoned.
Without the extra troops suggested by Kagan and Kagan, they say the fighting in Helmand will continue to be indecisive, and Kandahar will have to be ceded to the enemy. Alternatively it may become necessary to withdraw completely from Helmand, which would not only humiliate the British Army, but would also lead to a mass slaughter of those who cooperated with the ISAF forces. From a military standpoint at least, President Obama would appear to have very few choices.