Their mission is daunting. Fight terrorism, stop drug smugglers and intercept illegal entrants from the air, on the ground and at all ports of entry. The battle lines stretch for the thousands of miles, and sometimes all that stands between the combatants is a flimsy metal fence — or nothing at all. National Geographic's critically acclaimed series Border Wars follows officers and agents of U.S. Customs and Border Protection (CBP) and their critical battles at the most treacherous border crossings between the U.S. and Mexico. In season three, Border Wars goes even deeper inside the struggle as CBP fights an escalating drug-smuggling crisis fueled by big money, cartel rivalries and violence threatening to cross into our cities each day.