Chapter 2 introduces more complex environments and the first encounters with armored vehicles and early AI weapons. You'll need to start utilizing your R&D team to develop more advanced weapons and items. Pay attention to the mission briefings for hints on enemy types and recommended gear.
This is also where you'll begin to see the importance of a well-managed Mother Base. Strong R&D and Intel teams will make these missions significantly easier. Don't hesitate to replay earlier missions to gather more recruits or resources if you're struggling.
While Peace Walker emphasizes R&D management for tactical growth, Metal Gear Solid Delta: Snake Eater focuses on the raw, immediate survival mechanics found in Big Boss’s original jungle mission.