Defensive Bidding

♣ ♦ ♥ ♠

Defensive bidding is split into distinct  situations depending on opponents opening bid and your position:

Your RHO PASSed (2nd position)

You must bid according to BETA opening bids schema in 2nd position - just as you would have opened in 1st position.

Your RHO opened either 1♣ or 1♦, alerted as 2+ cards OR specified as 3+ cards

You bid according to these opening bids with our exquisite 'short minor' overcalls

Your RHO opened 1NT with a specified 3 point range

You bid according to BETA's defence to a 1NT opening.

Your opponent opened with a pre-emptive bid - weak 2s or 3+ level bids in suits of 7+ cards

See our defence when opponents attempts to derail us by robbing us of bidding space

Opening in 3rd position that's following a pass by partner and by your RHO

Still refer to our BETA standard openings: BETA opening bids
However a degree of tolerance is permitted like opening 1♠ with 4 good cards or lacking one HCP or perhaps opening 1N slightly short of the specification etc. Partner needs to be aware of a diminished spec of a 3rd hand opening and exercise due care. But all said and done it makes every sense to find a way to open that's close to the regular specification rather than PASS!

Opening in 4th position that's following three passes: by partner and by both opponents

Well open 1♠ by all means even being a point short for example. However  opening in a red suit may just lose you the hand when they compete in Spades! and given that HCP points are somewhat evenly distributed competing may now be disasterous too.
However openings such as 1NT (partner can PASS or utilise transfers 2♦ ♥or bid 2♣ to find your 4 card suit
Also with highly distributional hands with openings such as 3mi or 2♦ can be risked.
However Stronger openings such as 2♣, 2Ma, 2N must be declared.
Also 5-5+ hands bidding: 3♦ Majors, 3♣ Red suits or 2♦ with ♣ ♥ or ♦♠. Also with ♠♣ it would be opened with 1♠ anyways & ♣ rebid at the 3 level (with OR without a jump) must now show 5-5+. Also with 5-5+ in minors and minimal values it may be inadvisable to make a 1♦ opening followed by 3♣  unless stronger as opponents my now search a Major suit to compete in at the 3-level!
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