Before I describe the German invasion of Belgium, I must explain certain military terms which will crop up again and again in the following pages. Unless you understand these terms, you cannot read war news intelligently. An army, you know, is a body of armed men, trained and organized and disciplined for the work of war. Most of the fighting men in an army are either infantry, cavalry, or artillery. Let me tell you something about each of these "arms." _Infantry_ are foot-soldiers armed with rifles and bayonets. In time of peace you have seen them marching by in their scarlet and blue uniforms and smart spiked helmets. You have also seen the Highlanders, with their waving feather bonnets, short scarlet coats with yellow facings, white belts and gaiters, plaid stockings, and bare knees. In time of war all these fine uniforms are discarded, and the men are dressed in khaki. Every foot-soldier belongs to a _regiment_, and is one of a _company_ of that regiment. A company consists of 227 men of all ranks, and is commanded by a captain or major, with a captain as second in command. Every company is divided into four platoons under lieutenants, each of whom has a sergeant as second in command, and each platoon consists of four sections under junior sergeants, corporals, or lance-corporals. In the British Army four companies form a _battalion_, which has been well called the household or family to which the soldier belongs. It consists, when at war strength, of 1,007 men, including what is called headquarters--that is, the battalion staff, the men of the machine-gun section, the signallers, pioneers, and the bandsmen who in time of war serve as stretcher-bearers. A battalion is commanded by a lieutenant-colonel, who is assisted by a major, an adjutant, a quartermaster, together with a number of sergeants, orderlies, and clerks. The adjutant is specially responsible for the book-keeping of the battalion, for issuing the orders, and for seeing that all military duties are properly performed. The quartermaster has charge of the stores, clothing, and the equipment of the men. The strength of an infantry force is reckoned in battalions, not in regiments. Four battalions--that is, 4,000 men--form a _brigade_ of infantry, which is commanded by a brigadier-general, who is assisted by a brigade-major and a staff-captain.