Random Antiterrorism Measures

The Random Antiterrorism Measure (RAM) program uses random, multiple security measure that change the look of an installation’s force protection program and introduce uncertainty to defeat surveillance attempts and make it difficult for a terrorist to accurately predict security actions.

“A unit could conduct random antiterrorism measures by checking parking lots, conducting bag checks and ID cards in locations where that is not the normal security posture,” said Ann Moree, security manager, DPTMS.

This is basically what's going on. The theory is that by making changes to the process it will be more difficult for someone to plan a way to defeat it (not really true, as several TSA pentests have shown).

There's also this classic quote attributed to a German general during WWII:

War is Chaos, and the reason why the American Army excels at War is because they practice Chaos on a daily basis.

It may look like the front-line guys have no idea what's going on, and that might actually be true. If they have no idea what's going on, neither will anybody observing their activities.