Although this gang Headquarters takeover was classified as hard, it is actually quite easy once you know where to go and how to approach it.
Approach from the south and look for a pair of guards standing guard at an entrance. Walk up and double assassinate them before climbing on top of the building to the left of their position. Look back down to where you killed the two guards and stick on eagle vision – 80% of the time, the captain is going to be hiding in that haystack right next to them or in the stalking zone surrounding the nearby building, so air assassinate him to the max…
Return to the roof of the building we just jumped from and look across to the right to find the flag. Either wait for the sniper to patrol away from you or hit him with a sleep dart before jumping across to that roof and interacting with the flag to complete the second objective.
Now quickly jump from the rooftop towards the other two red markers. Run over and pop through the hole in the fence to enter a cane field, which happens to be one large stalking zone. From here you should be able to spot and shoot both poison gas reserves without being detected – just steer clear of the enemies when they look through the field (don’t worry there is plenty of space to outmanoeuvre them!)
Once all three objectives have been completed, the HQ will be all yours!