Discussions of World War I -- sometimes referred to as "The Great War," as people hadn't yet learned to number their global conflagations -- can focus on any of several areas. The first involves international relations from about 1879 to 1914, the year the war broke out. Secretive negotiations and alliances combined with ancient animosities over time established the foundation from which that war would emerge. That the assassination on June 28, 1914 of Archduke Franz Ferdinand of Austria by a Serbian nationalist would trigger the largest, most destructive war in history can only be understood in the context of the age-old balance-of-power politics that dominated international affairs. The origins of World War I are often traced to the 1870 reunification of Germany that followed Prussia's victory over France in the Franco-Prussian War. The emergence of a major power in the heart of Europe, and one with the industrial potential to dominate its neighbors, caused enormous anxiety among those neighbors.
Meanwhile, internal threats to the stabilty of the Austro-Hungarian Empire, mainly centered in Serbia, were pushing the Austrians closer to their natural brethren, the Germans. Combined with frictions over colonial ambitions and the opaque nature of diplomatic initiatives, the seeds were planted for a large-scale conflict.
Another potential topic for a paragraph or essay on World War I could be the way the war was fought: networks of trenches with human wave assaults countered by the newly-introduced machine guns and the use of chemical warfare in attempts to dislodge the enemy from its trenches and break the stalemates that were characteristic of the war. Additionally, this was the first war in which aircraft were systematically used to drop ordnance on enemy positions. The contrast of trenches and the introduction of new technologies of warfare is in itself a worthy topic of discussion.
Finally, the war's outcome, with the signing of the Treaty of Versaille, which planted the seeds for the next major European war, is a possible subject for a paragraph or essay on the war. The conditions imposed on Germany by the victorious British and French were sufficiently austere so as to ensure German disillusionment and resentment. Occuring in the context of economic collapse, those sentiments would prove disasterous, as they facilitated the rise of Adolf Hitler.
These, then, are three topic that can be used for a paragraph or more on World War I.