As for where these troops may be arriving from the answer is simple: that other US military intervention success story - Afghanistan. From Reuters:
The number of U.S. troops in Afghanistan may drop well below 10,000 - the minimum demanded by the U.S. military to train Afghan forces - as the longest war in American history winds down, Obama administration officials briefed on the matter say.
Since Afghanistan’s general election on April 5, White House, State Department and Pentagon officials have resumed discussions on how many American troops should remain after the current U.S.-led coalition ends its mission this year.
The decision to consider a small force, possibly less than 5,000 U.S. troops, reflects a belief among White House officials that Afghan security forces have evolved into a robust enough force to contain a still-potent Taliban-led insurgency. The small U.S. force that would remain could focus on counter-terrorism or training operations.
That belief, the officials say, is based partly on Afghanistan’s surprisingly smooth election, which has won international praise for its high turnout, estimated at 60 percent of 12 million eligible votes, and the failure of Taliban militants to stage high-profile attacks that day.
The Obama administration has been looking at options for a possible residual U.S. force for months.
"The discussion is very much alive," said one U.S. official who asked not to be identified. "They’re looking for additional options under 10,000" troops.
There are now about 33,000 U.S. troops in Afghanistan, down from 100,000 in 2011, when troop numbers peaked a decade into a conflict originally intended to deny al Qaeda sanctuary in Afghanistan after the September 11, 2001, attacks.
Of course, it would be peak irony if the next country Russia decides to destabilize is none other than its old “buddy” Afghanistan, which lately appears far more amicable toward the Kremlin than the White House. It certainly would be an additional egg in the face of US foreign policy if Aghaniitan - so critical to the US controlled heroin trade - were to show a return to some of its Taliban roots for which it is so well-known.