It's The Last Point At Which The US Thinks It Can Force Israel To Surrender.

https://www.jpost.com/israel-hamas-war/article-800944

They thought they would be able to impose that surrender after the devil Jews had sated their bloodlust in the North. They were wrong.

They thought they thought they could impose that surrender after the devil Jews had sated their bloodlust in the Centre. They were wrong. 

Once the South is under Israeli control the only way the US will be able to preserve any remnant of Hamas is by pivoting and imposing a surrender on Hamas.