Treaties after Great Wars can be incredibly brutal. Whilst certainly possible, do not assume the war will be over by Christmas. It is worth noting, however, that it is wise to draft war plans in advance and to prepare for a worst-case scenario. In conclusion, Great Wars can be strategically similar to normal wars. This would leave the resources completely out of the reach of their weakened allies, which in a few years would give you huge amounts of revenue from the automobile and aeroplane industries. While this will make them the victor and also determine the goals achieved, to what avail would it be if the country's man power stock was completely wiped? This would leave you, who took a step back, complete dominance of the global stage and be able to snag those ripe territories of newly discovered rubber and oil. You could not participate in large battles and let allies do most of the lifting. While this is dark it must be said, due to the mass amounts of casualties and damage a great war can do to both the victor and defeated it is a valid strategy to also undermine your allies. This is much better than, say, getting oneself into a "meat-grinder" (that is, a battle involving a huge number of troops with massive casualties) but if enough troops are available it might be a viable strategy to catch the enemy and use it as a distraction. Getting yourself into a single pitched battle is possibly the biggest mistake ever it is much better to spread your troops in medium stacks and look to whittle your enemy until a break in their defense appears.
Since Great powers have colonial nations overseas there is a tendency that they have huge manpower stocks leading to huge stacks of men being hurtled at each other. It is also imperative to establish a naval blockade on your enemies' coast for the faster war score increase to end the war sooner. You should always try to create a defensive line on strategically beneficial land. Using the landscape around is key - for example, Germany had the very wise decision to take all the high ground for a natural defense in the First World War this caused massive casualties against impeding British and French attacks. While it is good to try and create your own strategies to end a Great War it is wise to learn from the actual people who fought in the First World War. If possible, a quick drive into the heart of enemy territory once war is declared akin to that of Germany's Schlieffen plan can be a knock-out blow, but it is wise not to repeat the delusions of Germany in 1914 a defensive strategy must be considered. For this reason it is wise, just like the Great Powers in 1914, to mobilise quickly as soon as war looks inevitable. Great Wars can have severe effects on a nation's populace and economy, especially when fought on home soil. Aside from this, it can be very difficult to deliberately prevent outbreak, unless isolationism is simply opted for. For this reason, a player wishing to prevent the outbreak of a Great War must have mastery of any crises that emerge.
The most common cause for the outbreak of a Great War is a crisis, due to the fact they will often put multiple great powers against each other. A regular war becomes a Great war if it have minimum of 2 Great powers on each side, and great wars have been invented.