During conquest games on Sinai Desert, a armored train will occasionally spawn for 1 team.
I have only seen it spawn for the opposing team so far, once at the last minute of the game and once around 10 left.
At first i thought you had to control all or a specific map point to trigger it, but that has proven false in my experience.
Best Answer
Behemoths spawn at most once per map. They are given to the loosing team to "help turn the tide of the battle".
What exactly triggers them isn't 100% clear, though it's rumored that it's based on time and ticket gap.