S.O.G. - Intel 1
Find this intel in the open hill area, after you’ve destroyed the three tanks and before you drop down the hatch. It’s located in front of the long supply shed at the top of the hill.
S.O.G. - Intel 2
You’ll exit the tunnels and enter another big downhill section with waves of Vietcong soldiers attacking. In the midst of all the chaos, make your way down and to the left - there’s a large shelter near the bottom, with the intel sitting on a window sill. Since this area is relatively nonlinear, you should study the screens or watch the video for a more exact idea of its location.
S.O.G. - Intel 3
More tunnels, these full of injured U.S. soldiers and broken, burning structure beams. Right before you reach the brighter room with the American flag, check the darker corner to your right, near the soldier catching his breath. The intel is located on a lower shelf.
The Defector - Intel 1
See the mysterious projector and screen? Leave that room and halfway down the hall - on your right - will be a smaller room with a corpse on the floor and an intel on the green desk.
The Defector - Intel 2
At this point, you’ll be fighting through the streets of Ho Chi Minh City, supporting a tank and calling targets for a helicopter. Look for the building indicated in the first screen above - use the Vietnamese store signs for reference if necessary - and within you’ll find the intel on a desk under a clock.
The Defector - Intel 3
Near the end of the mission, you’ll be asked to hold position in a large town square as Vietcong attack through smoke screens. Before fighting them all off, find the building under the “DAK” billboard and enter through the torn hole in the wall. The intel is on a desk to the left.
Numbers - Intel 1
Your interrogation of Clarke has been very rudely interrupted, but before running forward to fight and climb the ladder, turn to your right and head into the side room full of messy papers and bulletin boards. The intel is here.
Numbers - Intel 2
Climb down the pipe, shoot the two unsuspecting soldiers from above, run across the rainy planks while Clarke tells you the location of Steiner and, finally, slide across the sloped rooftop in slow-motion as birds fly away. The intel is hidden behind the low wall in front of you, left side.
Numbers - Intel 3
Know the part at the end of the mission, when you slide down a ramp into an ambush? And survive only with a pistol until a van picks you up? Yeah, if you reached that part, you’ve already gone a little too far. Let yourself die so that the game reloads, then immediately before sliding down the last ramp - but immediately after jumping over the last balcony railing - turn 180 degrees around to discover the intel sitting within easy grasp on the ground behind you.