If everything is going against you and you have back to the wall, there will come a stage when you lose the strength to fight. That stage, when you no longer can take, is the one where you succumb, give in or put it a idiomatic manner, the walls cave in.
Meaning of Succumb
Master Tip to Learn Succumb
Think of the related word submit, as it means “to yield control.” Succumb means you have submitted to defeat. You have probably heard someone say, “I can’t believe you succumbed to their demands.” This statement is in fact one of the most common ways of using this word.
Sentence examples for Succumb:
1. He was determined not to succumb to temptation while on the diet.
2. After years of suffering, the man finally succumbed to his illness
3. The government was unlikely to succumb to the demands of the kidnappers.
4. I succumbed to his request, though I was not happy to do so.