This is a story related achievement and cannot be missed.
Once you crossed the brigde from the bridge from the previous chapter you will want go inside the house. After a dialogue aliens will start to attack. Fight them off and prophet will then want you to jump into a car and drive away. Once inside you will get a help call from Helena Rosenthal. Just worry about shooting cause the AI will drive you there. Next to the VTOL kill all approaching enemies until she is rescued. Afterwards a huge alien will come in sight. Instead of shooting it juast run off to the next green point on your radar. at the collection point shoot it with AA guns (though i don´t think you need to) and wait for your VTOL to land. Once you stepped inside Major Strickland will sacrifice himself and the achievement is yours.