Processing gain is finite. With enough wideband jamming power, or with a clever follower jammer that tracks the hops, a spread-spectrum link can still be disrupted. In practice it is therefore combined with coding, antenna nulling towards the jammer (compare CRPA for GNSS, GNSS and navigation warfare) and — increasingly — with the cognitive techniques from this chapter.
That is where the two concepts come together: spread spectrum makes a link hard to hit, and cognitive EW ensures that both attacker and defender adapt in real time whenever the other finds a trick. The common thread of modern EW is therefore adaptivity: nothing is fixed any more; everything learns, hops and adapts.
These two concepts explain why today's EW systems are software-centric. Spread spectrum is the antidote to much of the jamming from Electronic Counter Measures — it determines how much power you need and why some links seem “invulnerable”. Cognitive/adaptive EW is the next step beyond the threat library (EW: Electronic Support Measures): the speed at which you update your algorithms becomes a weapon in itself.