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

Red Dead Redemption 2 (stylized as Red Dead Redemption II) is a western-themed action-adventure video game developed and published by Rockstar Games. It is the third entry in the Red Dead series and a prequel to 2010's Red Dead Redemption and was released on October 26th, 2018 on PlayStation 4...

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

Red Dead Redemption 2 (stylized as Red Dead Redemption II) is a western-themed action-adventure video game developed and published by Rockstar Games. It is the third entry in the Red Dead series and a prequel to 2010's Red Dead Redemption and was released on October 26th, 2018 on PlayStation 4...

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