To forego, forfeit, surrender, lose — to give something up for something else more important. This theme of sacrifice is typically used in film as a way to develop characters quickly and gain sympathy from the audience. Large scale action movies invoke sacrifice when there is little time to fully develop the character arcs of a whole ensemble. Sacrifice is used so often and sometimes so thoughtlessly, it is easy to think of it as being ineffective. But there may yet be a way to use the sacrifice trope in a persuasive and compelling way.   

When is sacrifice effective?  

When well-presented, sacrifice can add depth to a drama. The “Harry Potter” films, based on the bestselling novels by J.K. Rowling, exemplify sacrifice as a meaningful act of love.   
harryWhen we first meet him, Harry Potter is a young orphaned boy living with his cruel Aunt and Uncle. On his eleventh birthday, Harry learns that he is actually a wizard, and that his magical parents were killed by an evil wizard named Voldemort. Voldemort also attempted to kill the infant Harry, but the spell mysteriously didn’t work, making Harry “the boy who lived.”    
The theme of sacrifice is gradually introduced to the audience over time as Harry and his friends Ron and Hermione grow closer with each film, and the mystery surrounding Harry’s survival of Lord Voldemort is solved: it is eventually revealed that Harry’s mother saved his life by sacrificing herself, her love acting as a barrier between Harry and the Dark Lord. 
As Harry gets older and is forced more and more to accept his role as ‘the chosen one,’ he becomes more willing to sacrifice himself for his friends, and they for him. It is Harry’s mentor, Professor Dumbledore, who offers the most controversial sacrifice of the series when he insists that Professor Snape take his life so that Voldemort will trust Snape completely. While one could argue the death of Dumbledore was unnecessary, both he and Snape agreed to make that sacrifice for Harry.  

How some films use sacrifice better than others 

In the “Harry Potter” films, sacrifice isn’t used to prove a character’s worth so much as it is meant to emphasize the bigger themes of love, friendship, and bravery.  
In contrast, Marvel’s “The Avengers” series, in its two-part grand finale, “Avengers: Infinity War” and “Avengers: Endgame,” specifically uses sacrifice to give certain characters some last-minute development.  
thanos_marvel_featureIn “Avengers: Infinity War,” we discover that the character Thanos is on a quest to acquire the six ‘infinity stones,’ which, when combined, will make it impossible for the Avengers to prevent him from destroying half the universe. Toward the end of the film, we are introduced to the planet ‘Vormir,’ which requires its visitors to sacrifice someone they love in order to retrieve the Soul Stone.  
Thanos, desperate to achieve his aim of ‘balancing’ the universe, sacrifices his daughter Gamora, and we are led to believe that he feels guilty about killing her. In this way, sacrifice is used primarily as a crutch to give Thanos character depth, as he is meant to be a more complex villain that viewers can empathize with, despite his intentions.  
In the final film, “Avengers: Endgame,” Black Widow and Hawkeye must face the same hard decision on Vormir. Both characters try to sacrifice themselves for one another, until Widow prevails, giving her life for Hawkeye’s, and helping the Avengers defeat Thanos. This scene, meant to complete Black Widow’s character arc — from Russian spy with no family, to finding her family in the Avengers — almost took the sacrifice element too far.  
The complex nature of ending an entire decade worth of films and character stories made it difficult to tie off each hero’s development arc, so perhaps the use of sacrifice is justified, even if it wasn’t the most effective use of it.  

Looking at sacrifice through the lens of war  

With our more advanced film technology, our war films today have been able to portray the true experience of sacrifice.  
Two very recent examples to highlight are “1917” (2019), and “Dunkirk” (2017). The directors of these films used technology to their advantage, giving the audience a real taste of what the young men who fought in world wars I and II experienced.  
For “1917,” director Sam Mendes joined forces with Oscar-winning cinematographer Roger Deakins to bring audiences a one shot film, bringing viewers down in the trenches with the soldiers, and not giving them a moment’s rest until the character’s journey is finished.   

Dunkirk-1917 “Dunkirk” also uses intense and immersive visuals and sound effects to give audiences a taste of the experience of World War II’s battle of Dunkirk.   
Fighting for one’s country is the ultimate sacrifice, and these stories, while compellingly told, don’t necessarily persuade viewers to sacrifice themselves for their country. They do evoke a sense of patriotism, and maybe admiration, but the sacrifice of countless young men often seems neither glorious nor justified.  
But that is not always the purpose of sacrifice as used in a portrayal of the bloody history of war. The sacrifice of soldiers in war films is employed less as a means by which to develop a character quickly, and more as a way to expose the true and harsh nature of war.  
Sacrifice can be a compelling device in a film to draw in an audience and develop more complex characters. It can be misused as a crutch when there needs to be a convenient reason for drama or explosive action. But a true artist knows how to place sacrifice in the heart of the film that makes a story more meaningful.