When walking a new dog or a rescue dog or even a friend's dog, be sure you have good grip on the lead and you have control of the lead NOT the dog.
If a dog pulls STOP walking and direct the dog to a sit position.
When the dog sits. Praise with a treat and a cheerful YES! Then say ok and continue the walk.
This lets the dog know that you are in control and they must listen when on walks and it prevents a dog from pulling your arm right off.
It's collecting them and redirecting there focus onto you again. Also another word to use is Leave It. You can say Leave It, direct them to sit and reward and continue on.
If the dog grabs the leash and usually wants to play. This considered a tug of war. NEVER let the dog win.
Direct the leash over and back and they will release and immediately put them in a sit with a firm command.
When walking I always suggest to have treats.
Aggressive in dogs can be a fine line. Especially when working with rescues.