First, ammunition supply.

If you go back to ancient times by tank and fight against the ancients, there is only unlimited fuel, and the tank cannot be damaged, which is far from enough. The most important thing is the source of ammunition, because ammunition is not unlimited. Limited ammunition is used up, where else can we get suitable ammunition? What's the difference between a tank without ammunition and a salted fish?

Second, manpower.

If you cross with tanks, who can you take with you except ammunition? If Tanqueray comes with a complete tank team, you will be lucky. If you+tank, congratulations, you are doomed to be exhausted in the tank mine. Don't try to teach the ancients to drive tanks. I'm glad I didn't sacrifice you to heaven.

Third, through the ages.

If you go back to before the Tang Dynasty, you are very lucky. At that time, guns were not very developed and there was no threat to you. You can be awesome for a while, but it is more difficult to solve the first problem. If you travel back to the Tang Dynasty, or the Middle Ages in Europe or even later, I can only advise you to be honest and keep a low profile. This period can be called the era of firearms, Mongolian monster cannon, European siege running and lizard rising.