If your opponents are of bad-tempered and irritable

That doesn't sound like proper English to me.

A translation:

“If your opponent is of choleric temper, seek to irritate him. Pretend to be weak, that he may grow arrogant.”

Or another:

“If your enemy is secure at all points, be prepared for him. If he is in superior strength, evade him. If your opponent is temperamental, seek to irritate him. Pretend to be weak, that he may grow arrogant. If he is taking his ease, give him no rest. If his forces are united, separate them. If sovereign and subject are in accord, put division between them. Attack him where he is unprepared, appear where you are not expected .”