If opponents make an overcall at one level over partner’s 1m opening, supporting the opening suit or bidding 1NT shows a hand that doesn’t have four cards in the unbid major or majors. As it is preferred to play a game contract in a major that we have eight cards it is also advantageous to play a part score contract in a minor that we have eight cards. With this in mind, it is a good choice to support partner’s minor with at least four cards after their overcall in order not to lose competition chance. If you bid 1NT over RHO’s overcall and LHO makes a bid at two level, partner with a minimum opening will allways pass. In the case that you support the opening minor instead of 1NT response, opener is most likely to continue the competition with a 5-card minor. Based on this logic, after RHO’s overcall, we can summarize the possible responses you can make as: