Having doubled the opponents, you now have to find the best way of enforcing your call. Are the odds so close that defeating the contract is the over-riding priority? But if the opponents' intention were to deprive you of a certain game you should be looking to inflict severe penalties.
These are the sort of questions that will face you in this quiz book of bridge problems. The deals have been chosen from major national and international championships. In almost every case you have the chance to do better than the defenders did at the table. As long as you tackle the problems with zeal and determination, your own defence is bound to improve, even if you do not find the best answer every time.