Thanks to: https://blog.activision.com/call-of-duty/2019-10/Feature-Explaining-Player-Progression-in-Call-of-Duty-Modern-Warfare for this information/post
Call of Duty: Modern Warfare is set to offer a fresh progression system that gives players a constant stream of rewards while keeping the satisfaction and pride that comes with ranking up.
Here’s the important Recap so you don't have to read for 5 minutes:
To reiterate how progression works in Call of Duty: Modern Warfare, you will:
· Rank up through the Enlisted Ranks (1-55) to unlock base weapons, perks, equipment, Killstreaks, and Field Upgrades.
TO UNLOCK MORE FOR YOUR BASE WEAPONS…
· Rank up your weapons individually though the weapon progression system. Gain experience for each weapon to earn attachments and base camouflage patterns, and complete camo challenges to complete camo sets.
THEN, AT THE START OF EACH SEASON OF CONTENT…
· Begin your Season of Officer Ranks, where you will receive an Officer Challenge at each rank leading up to 5-Star General (Rank 100). Completing each challenge rewards a ribbon. Earning 10 ribbons awards an Emblem, and all 100 ribbons gives you an even more badass Emblem.
AT THE END OF A SEASON…
· Officer Rank is reset, Enlisted Rank is not.
· Player XP can be earned through playing the game, completing Daily Challenges, Officer Challenges, Camo Challenges, and Challenge Missions; multi-step objectives that offer even more rewards upon completion.
· There is scheduled to be a number of seasons packed with tons of free content, where you will also progress through Officer Ranks.