Tanks
Following the breakthroughs of the World War I, most countries realised that the development of tanks would play an integral and vital part of any future war. However, what with the inter war years of depression, it wasn't until the outbreak of World War II that the real momentum for developing effective armour caught hold. Generally categorised into light, medium and heavy models, tanks offer the battlefield a veritable mobile strong point, which can be equally productive in both attack and defence.
A good tank needs to address three vital points; armour, weaponry and mobility. Like balancing the sides of an equilateral triangle, if one of these areas is given too much attention the other two will suffer. World War II witnessed rapid advances in tank design that led to some weapons of awesome ability, but the bugbear of these leviathan machines is their poor reliability; something which affects modern heavy armour even in the 21st century.
