The 5th Corps' combat strength was estimated at 30, 000 troops when the U.S.-led invasion of Iraq began March 20, but it is unknown what toll heavy airstrikes and desertions have taken on its three infantry divisions and one mechanized infantry division, U.S. military sources told CNN.

CNN: Coalition makes key advances in northern Iraq

Guardiola has the option of restoring Pique to his starting lineup to combat Drogba's strength, having sprung a surprise by leaving the Spain international out of both the first leg and the game against Madrid.

CNN: Barcelona have point to prove against Chelsea

Combat units would be increasingly under strength.

NPR: Army Recruiting Gap May Force Compromises