Whether you want to show support for the troops in an illustration, or just like creating exciting military action in art, drawing a military helmet is an essential subject. Despite the many types of military helmets, they all can be drawn from the same basic form. The ability to draw this form and adding some ornamentation to it is all that is needed to draw a military helmet.
Draw a circle. Divide the circle in half by drawing a horizontal line through it. The top half of the circle will be the basic shape for the helmet. Draw another horizontal line below the first, close to the middle. Connect the two lines by drawing a curve on each side that runs from the end of one line to the end of the other. This will make the circle appear three-dimensional as it gives the illusion that you are seeing through it. The two connected lines become an eclipse that represents the bottom of the helmet.
Study a photo reference for the type of military helmet you wish to draw. Use this as a guide and draw the helmet outline over the half-circle. Draw what you see by looking for the individual characteristics of the helmet's form. The helmet may not be as perfectly round as your circle and may have many other imperfections from wear. Express the individuality of the helmet shape by using contour drawing that captures the visible bumps and dents in it. Contour drawing is just another term for drawing the outline of something. Unlike the circle drawn from memory, contour drawing is made by referring to a reference of some sort. The goal is to create a realistic representation of the helmet with the contour drawing.
Add the details of the helmet such as texture and any accessories attached to the helmet. Texture can be expressed with cross hatched lines and shading. If you are drawing bumps, or raised areas of the helmet, hatched lines can be placed around the form to make it appear three-dimensional. Hatch marks can also be used to create the shadow of the bump. Shading can also be used instead of hatching to show forms such as this. Draw dents in the helmet by reversing the placement of the shading or hatching. Place the shading or hatching inside the dented area and leave the space around it lighter. Accessories such as goggles and straps on the helmet can be drawn on top of the circular form with contour drawing. Study the reference and draw the outlines as they appear. Shading or hatching can be added around these accessories in the same manner as the bumps, since these are all raised above the helmet surface.