Whoa, that was incredible! I can't even imagine how much hard work and repetition they must have done to get that right.
Less than you might think, takes time and effort certainly but trickiest bit is actually the choreography not the execution. Having competed and trained people for several marching competitions during my time at school I can say that once you have a group that has the key marching down perfectly and you have a squad that works well together executing this sort of thing is very doable.
Not to take anything away from this as they have mad skills, but I have seen better. Where they do do very well is the speed in certain parts, however being a stickler for marching etiquette the actual marching became much sloppier at those points. Either way mad skills
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