When Churchill reaches the words “We shall never surrender”, the word he puts the most stress on is “never”. Well, of course it is. He is not interested in stressing “surrender”; surrendering is what the British people are not going to do. He is interested in “never”.
He already has that runup to the critical four words, the “we shall fight them on the beaches” section. For an image of Britain under invasion, it’s extraordinarily powerful and inspiring. Remember that this was written and the speech given at a time when it was widely believed that the invasion would come within weeks; his message is that invasion is not the end, that even if Britain were to be invaded, it would not be the end of the war.
Then we get to those four words. He puts a bit of stress on We and Shall, but not too much; to mangle a metaphor, like a high jumper who has just performed a perfect run-up, this is the final foot-plant, the firm base for lift-off, but it’s not the point of it. The point is “never” and it’s on that word, and in particular on the first syllable, “NE“, that he really punches it, converts all that energy and forward momentum into vertical lift-off. “ver” is also stressed but not quite so much; it’s the smooth roll over the bar at the top. “Surrender” is the descent and landing; he doesn’t give it much stress of its own, but uses the momentum he’s already established. What he does do on “surrender”, if this makes any sense, is to keep it open, fluid, and fast. Stress at this point would slow things down and move meaning from “never” to “surrender”, so he doesn’t stress it particularly but he does use its rhythm and he puts a little uptick on the very last syllable, a little bounce, both of hope and defiance, and to carry him forward into the final section of the speech. These four words alone are a masterpiece of oratory.