It's a trench battle between SELL WALL vs BUY WALL here.
If first you don't break through, send in the second wave of attack. If that doesn't work, send in the third. If that still doesn't work, pull back and wait for reinforcement.
Now with ONT paratrooper as an ally, let's go at it again.
If BUY WALL don't succeed this time around, SELL WALL will push it way back into the deep BLUE resistance.