With a new Call of Duty game releasing every year, the franchise seems to both change dramatically yet stay the same with every release. New mechanics and weapons help spice up the frantic gunplay players love, but so much of the core franchise has stayed the same for ages.

Some of these mechanics were set in place since the first Call of Duty released back in 2003. The general gunplay of Call of Duty is as good today as it was when the first game released, but everything around its gameplay has changed radically over time. Here are 5 ways the Call of Duty series has both stayed the same and radically changed since its inception.

10 Changed: Realism

Once players get past Call of Duty’s aged graphics and mechanics, they’ll immediately notice the game’s focus on telling a realistic story.

Infinity Ward extensively researched as much about the setting as possible. Everything from the game’s animations to models depicts World War II as realistically as technology could allow. Coming off of the lone-wolf centric Medal of Honor series, the Infinity Ward devs sought to create a much more realistic depiction of war with an emphasis on working with others. Of course, this focus on realism has eroded with each successive entry.

9 Stayed The Same: Two Weapon System

Excluding the Specialist weapons introduced in Black Ops 3 and 4 that act as power weapons, Call of Duty has stuck with a two-weapon system since its inception.

What two weapons players use does not matter, but they can only carry two weapons at a time. Players typically start missions with a rifle and pistol, although they can scavenge for enemy weapons if the need arises. This system also extended to the multiplayer in every CoD title, although players would have to use certain perks or Wildcards in future CoD games to equip more powerful weapons in their secondary slot.

8 Changed: Health Regeneration

Many FPS fans have criticized Call of Duty’s “raspberry jam” effect when players get low on health. While annoying, it is an obvious indicator that the player is about to die and should enter cover to regenerate their health.

What most don’t know is that only the first Call of Duty and Call of Duty: WWII’s campaign are the only two instances where players didn’t have health regeneration. Instead, players had to find health packs throughout levels to regain their health. With the success of Halo’s partial regeneration system, Call of Duty 2 would mimic it and virtually every shooter has followed suit.

7 Stayed The Same: Action Setpieces

Shooters wouldn’t be as fun if they didn’t put the player into daring situations. Infinity Ward mastered this back when they worked on the Medal of Honor series, so they rightfully used those skills on the first Call of Duty.

From destroying V2 Rockets to charging the Reichstag with Soviet forces, Call of Duty’s campaign has plenty of high points that make it both memorable and fun. Virtually every Call of Duty title has included various action setpieces to keep each level adrenaline-fueled, from Call of Duty 4’s nuke mission to playing as Raul Menendez in Black Ops 2.

6 Changed: Setting

With titles such as Call of Duty: Advanced Warfare and Call of Duty: WWII sharing the same franchise, it is obvious that the Call of Duty series has changed its setting over the years.

The first Call of Duty started in World War II and would continue with that setting until Call of Duty 4: Modern Warfare would shift the franchise into a more modern setting. It shifted around this timeframe until Advanced Warfare brought the franchise further into the future where it would continue to do so until WWII. With the most recent release being a reboot of Modern Warfare in a modern setting, the franchise has now come full circle.

5 Stayed The Same: Friendly AI

A major shift from the Medal of Honor games, Call of Duty was focused more on the cumulative effort that soldiers brought to a battle rather than a lone-wolf that single-handedly ends a war.

While the shift towards lone-wolf gameplay is readily apparent, the usage of friendly AI to make campaign missions more engaging is still present today. Most Call of Duty games have doubled-down on this by making frequent friendly NPCs characters with full backstories that contribute to the game’s narrative.

4 Changed: Shift Towards Multiplayer

Many forget the time when Call of Duty was focused on providing a compelling campaign rather than innovating on competitive multiplayer.

Call of Duty 1 through 3 had multiplayer modes, but they were not as fleshed out as players expect from modern titles. Call of Duty 4: Modern Warfare’s inclusion of experience points, levels, perks, and Create-A-Class made for an addictive multiplayer component fans couldn’t get enough of. Ever since CoD 4, every game has made strides to innovate on its multiplayer with new features and modes.

3 Stayed The Same: Multi-Front Campaigns

Campaigns in most shooters focus on a single character that goes to a plethora of locations to fight bad guys. The formula certainly works, but it was getting formulaic around the time Call of Duty was made.

Starting with the first entry, nearly every CoD campaign has included multiple main characters into the story that portray different factions in the narrative. The first Call of Duty allowed players to experience World War II through the eyes of American, British, and Soviet soldiers. Nearly every campaign made after the first game has followed this approach with great success.

2 Changed: Popularity

Gamers forget that Call of Duty wasn’t always the juggernaut of FPS titles. Before Call of Duty blew up in popularity, most gamers spent their time fragging out in Halo or Unreal Tournament.

However, this all changed when Call of Duty 4: Modern Warfare released. The game’s revolutionary multiplayer components made for an addictive experience that other games in the genre couldn’t match. It rivaled other popular shooters at this point, but it cemented itself as a gaming juggernaut with the massive success of Modern Warfare 2, considered by many as one of the best Call of Duty titles ever made.

1 Stayed The Same: Engine

Excluding the most recent Call of Duty: Modern Warfare, every single Call of Duty game has been based on the id Tech 3 engine.

From the first game to Black Ops 4, every Call of Duty was using some form of the id Tech 3 engine to power their games. Call of Duty 2 and future games technically use the IW engine—an in house engine made by Infinity Ward—but much of the IW engine is based on the id Tech 3 engine used in the first game. This variant on id Tech would be used for every major Call of Duty title until Infinity Ward would create a new engine from scratch for the 2019 reboot of Modern Warfare. For anyone wondering why Modern Warfare feels so different from previous titles, this is likely the reason.

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