AFAIK the standard pronunciation is on the second syllable, both in AE (de'fense) and in BE (de'fence).

In AE, you will also very often hear 'de-fense (and 'of-fense', which is the standard (colloquial) pronunciation in the context of (strategy in) American football.

The first syllable isn't usually accented in other contexts, though. It's always, for example, the de'fense industry (companies that make military weapons), and the Department of De'fense. In a courtroom it's the prosecution vs. the de'fense, and people speak out 'in de'fense of' values such as liberty or human rights.

danke!

Hi hm!

I agree with your comments and would like to add that it's not only in American football, but also in basketball and other sports.

FWIW, here's a link to the website of one Paul Brians, the author of a book called "Common Errors in English Usage":

The pronunciation used in sports which accents the first syllable (“DEE-fense”) should not be used when discussing military, legal, or other sorts of defense.

http://www.wsu.edu/~brians/errors/defence.html

Hi, Jalapeño. (-: (OT: Have you all outgrown stroller/pram #1 yet? (-; )

Yes, very true. I thought of that belatedly (after another cup of coffee) but decided it might look a tad too anal if I posted again only to say that. But I'm glad you did. (-;

And also in some figurative contexts that feel similar to sports, e.g.,

The best 'defense is a good 'offense.

All sports, sure, but I am not sure about "The best 'defense is a good 'offense."

Bist du dir da 100% sicher?

It's true that it would sound more formal to say 'The best de'fense ...' And that pronunciation is preferable in other similar sayings, like 'Prevention is the best de'fense.' (Though many Americans would accent the first syllable there too, which is why Paul Brians has to remind them it's better not to.)

But 'offense' may be somewhat different, because of'fense means a crime or violation: a criminal of'fense, an of'fense against reason/decency, etc. (A criminal 'offense' might be one that couldn't make a single first down or score a single basket. (-; ) So when the two words are paired or contrasted, the first-syllable pronunciation may be more likely.

Where the exact line falls may be different for different people. Maybe some other AE speakers can help think of a few other examples.