One of my most-memorable experiences of the Vietnam War(time) occurred while I was a member of the drill team of an ROTC unit on the campus of the university from which I hold a bachelor’s degree, received together with a commission in the armed forces of the United States. We 24 or so cadets were practicing, marching in ranks of four along a paved campus footpath, from which we were accustomed to seeing individual pedestrians step off to let us pass. One such pedestrian, a male perhaps a bit cheekier than the others, noting our ordered files, sought to let us pass around him without his having to step off the path, turning himself sideways so that we might slip around him without breaking formation.
Our commander, in a split-second decision, deployed us against this interloper by ordering us (we were all carrying deactivated rifles) to Port Arms. We normally marched, as such units always do, at Shoulder Arms, in which our rifles were canted over our right shoulders. At Port Arms, however, we could continue marching, but we held our rifles diagonally across our chests, the butts protruding slightly to our left, and the barrels slightly to our right. This prevented our (passive) "attacker" from "penetrating" our ranks.
It was thrilling (for me, at least, in a trailing rank not dealing directly with the "interloper"). Our notional attacker was somehow thrust off the pavement, without even being knocked down as I recall, and we passed unpenetrated, as it were, while our interloper shook himself free of surprise and indignation by the side of "our" pavement. I found the total success of our synchronized execution of a single command most gratifying.