What horse? War Horse? Right war, wrong creature. You will be thrown by this play, like a rider into the mire, for its anger and sincerity are unbridled. All is definitely not quiet on the Western Front: in fact, it's a vicious mess. And the Horse You Rode in On takes singular aim at the grossness of the 'Great War', one hundred years on, and it doesn't miss - although credibility gets wounded here and there.

Arguably 1914-18 is by now a soft and indefensible target, but student writer/director Tom Stuchfield makes the most of that fact, with both strong action and concentrated character work. Two twenty-minute scenes are played in a dugout with a single sandbagged entrance. A third is laid in amongst the shell holes, the remains of another futile attack. There are low whiz-bang noises, the occasional whistle, and the onset of a rolling barrage that gets closer. "Yours? Ours? Doesn't matter." What does matter, of course, are the men underneath the gunfire.

And they don't care much, except for each other when it hurts, because they are horribly used to it and they cannot stop it. The war is well advanced and - crucially - discipline is in retreat. That's where the clear-as-mud show name comes in. Exhausted troops have had enough. NCOs and junior officers struggle for respect, let alone command. Spit and polish drills are a joke. The "Sir" word is shot. And now, if you still don't know what "And the horse you rode in on" means, Google it.

Shot on both sides. There's the neat device; Stuchfield's five-man cast play German and British soldiers, in doubled-up roles in shared time. Sergeants Meinhard and Wilkinson (Will Peck) resort to brute force and deceit; Captain Urban (Raphael Wakefield) is a useless martinet, while 2nd Lieutenant Dixon (Wakefield again) is "young, enthusiastic and [tries] very hard" but is just as ineffectual. For Everhart and Fletcher (Jonny Falconer), irony is a choice weapon.

But most developed of all are Spencer (Marcus Martin) and Volker (Chris Born), who have enough quiet minutes to tell their own back-stories. Born, especially, acts convincingly beyond his years as he remembers wife and home.

There are issues with the staging. The last scene has both actors on the ground, and it is none too easy to see them if you are just a few rows back. The venue's three pillars get in the way as well; so if you can, check your sight lines before you choose a seat. The play's ending, therefore, was concealed rather than obscure, but I understood enough amidst sound and fury to know that it was grim.

I have to say that I was looking for a touch of elegy - Wilfred Owen's 'Strange Meeting' came to mind - but that, sadly, was blown away by a snatch at Tarantino's 'Inglourious Basterds'. However, what came next was beautiful and fitting: an original arrangement by Raphael Wakefield of the Shaker song, 'Lay Me Low', which - on 4 August 1914 or 2014 - is a bullet to the heart.