August 20th:
Western Front: The Germans being a counterattack against the French in Lorraine. German heavy artillery outclasses anything the French can throw at it and the German army throws the French back to Nancy, erasing all gains the French had made, although the Germans fail to follow up quickly enough and the French are able to get entrenched in solid positions.
Brussels is occupied by the Germans, who march through to display all their military might.
Eastern Front: The Battle of Gumbinnen-After some skirmishing on the previous night, the German 8th Army (made up mostly of native East Prussians) under Maximilian von Prittwitz (dat name) moved into position to attack the Russian 1st Army under command of the mustachioed Paul von Rennenkampf.
The Russians were well aware of the German intentions and were able to set up strong positions. The entire battle was effectively dictated by the Russian artillery formations, which had long been the most effective part of the Tsar’s armies.
German general François’s corps was able to push back the Russian 28th division, after the latter’s artillery ran out of ammunition after whipping out the first waves of Germans (German infantry still tended to attack in column formation, leading to deadly results when faced with artillery). Their artillery out of action (the Russian armies effectively had no logistics, with the men surviving with what they had with them when they were ordered to advance), the 28th Divisions was mauled by the Germans until the 29th showed up later to stabilize the line.
Else where on the front though, Russian artillery and well dug in infantry blunted the other German corps advance, and counter attacked. The Germans completely broke and ran away in a mob like panic more often associated with the Russian army. 6,00 prisoners were taken and the German 8th army thrown back.
However, using up almost all of their ammunition, and taking a fair few casualties of their own, the Russians decided to consolidate their positions and wait for a logistics line to be established. This would have disastrous consequences, when Russian Theater Commander Yakov Zhilinskiy ordered the Russian 2nd Army under Samanov to advance without protection from the 1st Army, eventually allowing the Germans to concentrate their forces against it.
East Africa: The German forces push the British out of a small town called Taveta and cut the Ugandan railway.