From a reader:

Prior to Gulf War 2, our closest bases were in places like Turkey,
Bahrain, and Saudi Arabia. Assuming you can get enough troops in
country in the first place, every time they move must be carefully
reported to the host country. Want to send a helicopter of troops for
a sight-seeing trip along the Iran border? Better file a flight plan
with the international aviation community.
Now that we have bases in Iraq and don’t have all those pesky issues
with the host nation, it’s a lot easier for a helicopter full of
odd-looking people to disappear for a few days. Is there a higher
incidence of unexplained accidents in Iran or Syria? Do we have a
level of local insight that couldn’t come from anything other than the
“man on the street”?
I don’t think either of us will know the answers for another 50 or 60
years (look how long it took for Venona and Magic information to be
released). But it’s easy to see how having bases in Iraq and
Afghanistan provides a huge potential advantage to us, and how Iran
and Syria could be quietly pressured into more “helpful” positions.