What was the strategy of the north vietnamese in the vietnam war

The North Vietnamese strategy (before the U.S. pulled troops): guerrilla warfare and traps

The North Vietnamese strategy (after the U.S. pulls troops): organized warfare with tanks, infantry

Well it was more hit and run attacks this is why they had underground bases so they could hit the US or South Vietnamese troops then get back in the caves which allowed them to avoid the United States bomb and in the air it was very similar, they would have fighters ready to go and would only station them near important areas because they didn't have many fighters to challenge the US forces whenever they crossed the border. Instead they used SAM ( Surface to Air Missiles ) sites to defend these areas fighters would be to risky to use.