Lucas advocates to the silent era of filmmaking through (for example) the Griffith-ian crosscutting (see A Corner in Wheat as a brief example), while in some intervals during his prequel trilogy of Star Wars is a resource Lucas makes great use of, for now I want to analyze (or try to) how he particularly keeps intercutting during the duel between Anakin and Obi-Wan’s fight with Yoda and Palpatine’s.
The Griffith-ian cross-cutting is to refer Griffith a filmmaker of the silent era who is basically the father of editing and inspired soviet montage. Cross-cutting is a technique to cut between two events taking place at the same time on different places, besides the previously mentioned A Corner in Wheat, Intolerance is a fine example as he juxtaposes several events separated by centuries at the same time to indicate their correlation:
Quite like Griffith, Lucas uses this as both a thematic and narrative tool. Not only this helps us to visualize that these events are taking place at the same time, above all it works in a thematic level: the confrontation in Mustafar is the one between two “brothers” and the rupture of a marriage while the one on the Senate is between two adversaries, through this crosscutting we are displayed that this tragedy is working on two levels: in a personal manner and a social one.
Key to notice as well are the settings Lucas puts in display. In Mustafar a tone of orange and red is predominant. The use of fire or lava is a visual motif Lucas carries on during his movies. Notice in Attack of the Clones both the dead of Anakin's mom and his declaration of love towards Padmé are staged equally in which we have a fire at the left with the characters framed in the right and is the only two scenes of the film in which fire is displayed so their meaning is the most relevant due to comparison. Also Lucas always opens up with an objective point of view, large or extreme large shot; this is absolutely intentional to allow for visual comparisons to carry thematic.
We can say in both of those scenes Anakin is ceding to his passions... following his attachments, such is his flaw of the tragic hero: the incapability of balance leaving a path to an extremely passionate character. Is no coincidental that Anakin dies figuratively burning alive to become Darth Vader and that during the funeral in Return of the Jedi Luke burnt the body of his dead father, is a visual closure of arcs. Anakin succumbed to his love for a relative in both trilogies: for his wife in the prequels and for his son in the originals, is not that love is to be vilified but it juxtaposes the situation: on the prequels Anakin’s selfless love is transfigured into selfishness by the manipulation of Palpatine while in the originals that same selfishness is back again converted into selflessness due to an act of benevolence thanks to the influence of Luke. Moreover notice the funeral of Qui-Gon in Phantom Menace: the first person who showed benevolence to Anakin is destroyed by the burning passion that determines the Sith, is the lack of control thereof the one that determined the outcome of something sane: love. The Jedi forbid emotions making themselves detached and ignoring the evident problem of it, while the Sith exploit it to a point of selfishness and self-absorvance.
Is no wonder that said balance of the Force through the prophecy of the Chosen One (Anakin) starts with something that seem unfavorable for the Jedi: their own destruction. During the original trilogy we see a change in the manners of the Jedi, their narrow and detached tradition is left aside embracing emotion but with equilibrium, and later the Sith are destroyed by Anakin. Balance is described as a condition in which different elements are equal. Yoda himself admitted in Attack of the Clones that the Jedi have grown arrogant and Qui-Gon perceived that they lost their touch, we can argument then that by wiping both the Sith who brought everyone to an estate of chaos and the Jedi who were under a nanny state to a point of hypocrisy such balance was gained to start an equilibrium and correct a path, as Luke demonstrated being a new outbreak of the Jedi but taking into notice their flaws.
Back to Revenge of the Sith, notice when Anakin chokes Padmé: he is staged in the right side of Padmé like their declaration of love only that now that fire that was just ignited in Attack of the Clones is converted to lava, it is indicating that he is completely moved by his passion, actually is overflowing him.
And take a look over how Lucas implements the sabers, is known to everyone a Jedi (an acclaimed good side) wields a blue or green saber, as I stated the red is depicting a flaw, something overtaking Anakin. During the duel in Mustafar Lucas uses a great amount of either extreme long shots or long shots while variating the angles of the camera -mostly sticks to high and aerials when extreme/long shots are used and eye level when close ups are implemented, avoiding subjective perspective and creating a phenomenon in which we perceive mostly through an objective perspective in which we can see several rhythmic patterns implemented through juxtaposition.
Aerial shot
High Level shot
Shot reverse shot, eye level.
Notice how Lucas during the duel of Mustafar could give a dynamic of superiority to one of the characters by implementing a high shot and low one on the other but avoids this keeping the conflict neutral. He does the opposite with Yoda and Palpatine in which Palpatine is featured with a low angle several times, this is thematically important the only one coming out victorious is Palpatine even if Obi-Wan defeated Anakin, his triumph remains neutral.
However during Mustafar no matter the type of angle the overwhelming color displayed in the backdrop becomes the main subject, its predominance is a fact while "inside of the picture" both Anakin and Obi-Wan are barely the focus anymore but most noticeably the color blue of the sabers is lost, encompassing in a literal visual and abstract way the psyche of Anakin. Much like Ford uses landscapes to shape psychology, Lucas uses this resource in a highly expressionistic way presenting a constant decadence and submission of the blue or the goodness of Anakin and as I stated in a social regard as well: a democracy turned into a dictatorship, both juxtaposed ideas.
The cut also emphasizes this, notice in the clip bellow as Palpatine strikes Yoda it cuts to Anakin striking Obi-Wan: the goodness that existed in Anakin is being subjugated so is the Republic.
Lucas always crops when the evil party is striking and puts the other part being subdued. Bellow Anakin kicks Obi-Wan and we starts with Yoda falling on the next shot. He does this through all the fight and the Senate literally being use as puppetry by Palpatine do I need to explain?