With federal agents and the best bounty hunters in the nation massing on their heels

[mrmvp]

Does "with" mean "because" and If I change "with" to "because" is it correct?

With federal agents and the best bounty hunters in the nation massing on their heels, the gang must rob, steal and fight their way across the rugged heartland of America in order to survive.

Another question does "massing on their heels" mean the bounty hunters are in a large number to chase the gang.

Red Dead Redemption 2

America, 1899. The end of the Wild West era has begun. After a robbery goes badly wrong in the western town of Blackwater, Arthur Morgan and the Van der Linde gang are forced to flee. With federal agents and the best bounty hunters in the nation massing on their heels, the gang must rob, steal...

reddead.fandom.com

 

[Skrej]

Does "with" mean "because" and If I change "with" to "because" is it correct? No and no.

With federal agents and the best bounty hunters in the nation massing on their heels, the gang must rob, steal and fight their way across the rugged heartland of America in order to survive.

Another question does "massing on their heels" mean the bounty hunters are in a large number to chase the gang Basically, yes, although the large group chasing the gang is a mixture of both bounty hunters and federal agents, not just bounty hunters.

Red Dead Redemption 2

America, 1899. The end of the Wild West era has begun. After a robbery goes badly wrong in the western town of Blackwater, Arthur Morgan and the Van der Linde gang are forced to flee. With federal agents and the best bounty hunters in the nation massing on their heels, the gang must rob, steal...

reddead.fandom.com

See above.

 

[teechar]

Does "with" mean "because"

Roughly, yes. It means given those circumstances.

and If I change "with" to "because" is it correct?

"because" shows a more direct causal relationship, whereas "with" explains the context/circumstances that are (directly or indirectly and to whatever extent) contributing to the result.

 

[5jj]

16. PREPOSITION
You use with to introduce a current situation that is a factor affecting another situation.
With all the courses available, there is no excuse for not getting some training.
With the win, the U.S. reclaimed the cup for the first time since 1985.

https://www.collinsdictionary.com/dictionary/english/with