Throughout Star Wars: The Clone Wars, Captain Rex’s armor has an increasing number of tally marks. At first, fans might assume those marks represent kills. However, while that explanation was the original one, later episodes reveal that meaning no longer is canon. By changing the meaning of the tally marks on Rex's armor, The Clone Wars has created new possibilities for Rex's character.
The Clone Wars co-creator Dave Filoni confirmed in a 2011 interview with IGN that the tally marks represented kills. "[Rex is], like, this veteran now," he said, "and he's got little kill marks all over his armor." He added, "Rex doesn't believe that the new armor is really that good. [...] So Rex cut his old helmet up and welded together parts of the new helmet and his armor is a hodgepodge of old gear and new gear." Thus, even though the original explanation for the tally marks is more conventional, Rex's armor itself is unconventional and uniquely suited to his own needs.
Star Wars Rebels' Explanation for Rex's Tally Marks
While Star Wars Rebels kept Rex's tendency to mix and match his armor canon, the show contradicted the explanation for the tally marks five years later. In the Season 3 episode “The Last Battle,” written by Brent Friedman, Zeb asked Rex how many battle droids he shot during the war. Rex responded, “I don’t know. Thousands. Probably tens of thousands. Never kept count like some of the boys.” Thus, Rex pointed out an inherent flaw in the original explanation for the tallies: he killed too many battle droids to account for all of them. While the tally marks could have represented significant kills, this statement from Rex showed that his focus was never on his number of kills or battlefield glory.
One particularly poignant explanation of what the tallies mean might be that they represent the soldiers he lost in the war. That tracks with Rex’s increasing sorrow over his lost comrades throughout the war and his desperation to save Echo even when most people believed that Echo was dead. However, the Bad Batch arc of The Clone Wars both supports and negates this theory. That story focused heavily on Rex's survivor's guilt. He told Anakin Skywalker, "Sir, I have watched so many of my brothers fall during this war, and I try not to hang on to any one of them."
That statement might suggest that the tally marks may not be fallen comrades because, if Rex is trying to let their deaths go, he might not want to wear a reminder of them at all times. However, the use of "try" here is significant. It implies Rex is not successful at letting go, meaning this explanation could still be true.
The Tally Marks Represent Captain Rex's Growth
Another explanation might have been suggested in The Bad Batch. After returning home to their quarters on Kamino in the debut episode, Wrecker immediately starts making tally marks, indicating they're a tradition for Clone Force 99. Wrecker says, "Eleven more successful missions. Like there was any doubt," confirming the tallies represent missions, not kills. Like Wrecker and the rest of Clone Force 99, Rex might use the tallies to count mission successes.
Even though the canon meaning of the tally marks is unclear, the fact that the meaning was changed shows an evolving sense of Rex's character as more episodes of The Clone Wars and Star Wars Rebels aired. While Rex's loyalty and devotion to a cause bigger than himself have always been major parts of his character, these qualities received even more attention as the series continued. Between the IGN interview and the Star Wars Rebels episode, The Clone Wars aired multiple arcs that focused on Rex's leadership and loyalty to his allies. Ultimately, the people Rex fought for and with mattered more to him than any glory he might receive for his actions in battle.
While the audience doesn't know the full story behind Rex’s tally marks, they still represent an important character detail that illustrates his growth throughout the franchise. With Rex possibly appearing in the upcoming live-action series Ahsoka, fans may still get canon confirmation for the real meaning of the tally marks soon. But by changing the meaning of the marks, Friedman, Filoni and Star Wars' other writers allowed for the possibility of an explanation that might be more uniquely suited to Rex's character.