Mohan

Mohan is used to intervene over opponents' 1NT opening. Typically it only applies if the opponents' are using a weak 1NT opening (where 15 points or less is the maximum). Its invention is usually attributed to John Mohan.

Over 1NT:

• Double shows 14+ points, and is often left in for penalty. If it is not, the advancer (partner of doubler) bids as though his partner had opened 1NT. (Stayman and Jacoby transfers apply, for example). 2 shows both majors, possibly 5-4. If responder does not have a preference, he bids 2♦ to let opener pick.
• 2 is a transfer to hearts
• 2 is a transfer to spades
• 2 shows spades and a minor
• 2NT shows hearts and a minor
• 3 of a minor shows a long minor and is constructive
• 3 of a major is pre-emptive

Mohan’s Advantages

Since Overcaller is usually not bidding his real suit, it is hard for Responder to double or even bid if Overcaller has bid his suit.

Advancer often becomes Declarer forcing Opener to lead away from his strength.

When to Interfere

Consider interfering with any hand that you would have opened (one bid, weak 2, etc.).

Beware of bidding with square hands and less than 15 points unless you have both major.

After 1NT Doubled

After the weak NT is doubled, Advancer has many choices depending on the Runout strategy employed by Opener’s side.

If Responder makes a business redouble and Advancer does not have values to leave the double in, then he may transfer or use Garbage Stayman pretending that Overcaller had opened a strong NT.

If Responder passes the double starting a possible runout (Opener expected to redouble or bid a 5-card suit), Advancer can pass hoping for a later penalty double or bid (systems on) depending on his strength and distribution.

After 2 Overcall

• 2 - Shows little or no preference of a major (helpful if Overcaller is 4-5 in majors)
• 2 of major – Shows minimal values
• 3 of major – shows invitational values
• 2 Followed by 3 - Forcing
• 3 - To play
• 2NT – Invitational and natural

After 2 or 2 - Transfer

• Transfer should be accepted if Responder passes.
• New suit bid is natural and forcing 1 round.
• 2NT is a natural game try.
• Jump acceptances are invitational not forcing.
• Note if Overcaller then rebids a minor (including diamonds) he promises 4 in major and 6 in minor.

After 2 (Spades + Minor)

• 2NT- Game try asking size and minor suit
• 3 - Pass or correct
• 3 - Invitational

After 2NT (Hearts + Minor)
• 3 - Pass or correct
• 3 - Natural and forward going
• 3 - To play
• 3 - Natural and forcing