The Hessian Renegades is a key film in Griffith's early career. It doesn't really introduce anything new, but it is a particularly well-executed example of the uncomplicated action pieces that he had turned his developing style upon. It also hints towards many of the more advanced techniques he would later incorporate.
Griffith's experimentation at this time was mostly around the psychological impact of space and depth. Griffith realised that while the edges of the frame imposed stage-like limits (cameras did not move much in those days), the field of depth did not. In the opening burst of action we see a chase in which pursuer and pursued run towards the camera. This not only makes the most of the static camera position, but also involves the audience by having us overwhelmed by the enemy soldiers. You can see similar shots in Nursing a Viper which was made around the same time. It's likely these chase scenes lead indirectly to the development of the close-up, as for a brief instant faces are brought menacingly close to the screen.
Effective as it is, this kind of chase shot was more or less unique to its time in Griffith's cinema. Later chases would involve dynamic cross-cutting. Here however the editing is purely functional, to show changes from one location to another as the story demands. The central suspense scene - in which the soldiers search for the hidden messenger, is mostly done in one take because it mostly goes in one room. Griffith does of course begin parallel editing in the action-filled finale - but again this is largely functional, because he is showing different things going on in different places at the same time. Griffith must have noticed however that this actually made the sequence more exciting, because soon after this he would start to use parallel editing as a tension-building technique. The suspense sequence is actually one of the last long takes in Griffith's career.
What is really great about Hessian Renegades though is how purely visual it is. There are only two intertitles - one at the beginning and one at the end. The bulk of the story is conveyed through the acting, and all without resorting to the over-the-top pantomiming that mars many early films.
It's clear that some kind of visual language is beginning to appear. Of course, the importance of the Biograph shorts has mostly been realised in retrospect, but still it was around this time that Griffith was beginning to be recognised as an outstanding filmmaker.