Troop numbers
Some statistics from an Army Times article on deployments and troop number issues.
Total number of military personnel deployed in Afghanistan and Iraq since 2001: 1,406,281.
Number of actual deployments, including repeat tours: over 2 million.
The article has some very detailed discussion of the problems involved in sustaining sufficient manpower in these wars, and it's worth bookmarking.
A few more numbers:
Total deaths in both wars due to hostile action since the start of the war in Afghanistan: 2,553
Death rate: 0.18 percent, or 1 in 555, or about 180 per 100,000.