need help in a sniper nest assault

[Nightblade]

Hello,

I am playing the Vietnam campaign that comes with WinSP:MBT.

On the first battle, i "bought" some marine squads with Iroquois helicopters and a SEAL team + pathfinder.
Approaching carefully (1 case each turns) the objectives of the middle of the map , i noticed 3 squads of vietcong units entrenched.

My Iroquois opened fire with their machineguns , enough to put the vietcong units in "retreat" or "rout" behaviour , so i could make an approach with 2 Marine squads .

We took the position rather easily and destroyed the entrenched vietcongs squads, thanks to the support fire from the Iroquois.

But when i tried to continue the 1 case by turn movement toward the objective , one of the Marine squad "revealed" a distant spider nest (in fact when the snider nest opened fire on my squad).

After noticing this nest was able to fire to every directions, i tried an approach from the forest (as it was the only cover available) while 3 of my Iroquois fired at the nest each turn (the other were patrolling to see if any enemy units were around).

I lost a whole Marine squad in a turn after they came in contact to this nest (i made the mistake to -not- notice that the Iroquois rain of bullets was in fact totally useless) and before they could open fire , thanks to the booby traps the guys from the nest throwed at us.
I decided to learn the lesson and launched a smoke grenade in the case (adjacent to the nest) i wanted my other Marine squad to attack.

It was there that i noticed the Iroquois fires were totally useless in every ways against those sniper nest, unlike what they did with the entrenched units (of course no penetration but i was not counting on this, but the nest was always in "ready, dug in" state despite all the Iroquois bullets going in its hexagon each turns).

Hoping that the smoke would be enough if the bullets were useless, i launched the smoke grenade then moved to the smoked case (1 case by turns, always) and again i lost the whole Marine squad with this damn "booby trap" attack from the sniper nest.

In the south , i applied the same exact "cautious move in forest" + "smoke before attack" in the adjacent hexagon to finally destroy successfully (with a seal team) a bunker (not a sniper nest) without a loss.

So here is the question : while i think i have the good tactic to destroy bunker with minimum casualties (as my assault in the south of the map showed) ,i am clueless on how to approach and destroy a sniper nest in this vietnam era of the campaign without artillery and no apc/tanks/AT units.
Is there something i overlooked ?

In any case, i welcome any tactical help on this situation.