- General d'Urbal issues new orders for his 10th Army today, incorporating the revised instructions from General Foch. He envisions a series of methodical attacks, each designed to seize a particular objective from which the next assaut would be launched, culminating with the seizure of Vimy Ridge. In the centre, XXXIII Corps was to capture five points before launching its main attack on the village of Souchez, while XXI Corps had three positions of its own to occupy before assisting XXXIII Corps to seize Souchez. The first of these attacks is scheduled to begin tomorrow. On the German side, the units holding the line have gotten hopelessly mixed up over the past week, as companies and battalions have been sent haphazardly to plug gaps in the line and confront the main French assaults. As such, most of the day is devoted to reorganizing the defence, and in particular to straightening out the chain of command for the artillery batteries so that each stretch of the front line had dedicated artillery support. The battered 58th Division is also pulled out of the line, replaced by 16th Division.
To the north, the British 2nd Division launches an attack at dawn near Festubert, and a small amount of progress is made. For the rest of the day British artillery pound the German lines, in preparation for another effort tomorrow.
- As a result of the success of the German offensive at Gorlice-Tarnow, the Russian line in central Poland has been pulled back, to avoid a gap opening between the Russian 4th Army, mostly north of the Vistula River, and 3rd Army to the south. Following the Russians are the Austro-Hungarian 1st Army and an army group under German General Remus von Woyrsch composed of both German and Austro-Hungarian units. As the two forces pursue the retreating Russians, Woyrsch's group is pulled to the northeast, while 1st Army moves to the east, opening a small gap between them. Here, near Opatow, the Russian 4th Army counterattacks today, and the Austro-Hungarian 25th Division is thrown back several kilometres and suffers heavy casualties. The sudden Russian riposte brings Woyrsch's group and 1st Army to halt as they move to contain the unexpected enemy advance.
|The Battle of Opatow, May 16th to 20th, 1915.|
- Along the San River the German 11th Army attempt several crossings. The main action is at Jaroslau, which is occupied today by the German 2nd Guard Division. Here the town's Jewish population warns the Germans that the Russians have mined the bridge over the San, and shortly thereafter the bridge explodes and falls into the river. The Elisabeth Regiment of 2nd Guard Division then crosses the San at 530pm under the protection of heavy artillery and machine gun fire, and by evening a Russian counterattack has been driven off and the bridgehead is secure. To the north, 92nd Regiment of 20th Division is able to cross the San west of Miazownica, giving X Corps a shallow bridgehead. Thus by the end of the day, 11th Army has breached the river line at two places.
|The advance of the German and Austro-Hungarian armies at Jaroslau and Przemysl, May 16th to 20th, 1915.|
- In Italy the 'Radiant Days of May' are already passing; though a large pro-war demonstration grips the capital today, elsewhere the number and size of such gatherings are in decline. Despite its ephemeral nature, the 'Radiant Days' have completely altered the balance of interventionist vs neutralist opinion among the political classes in favour of the former. After Salandra's resignation on the 13th, Victor Emmanuel had canvassed several other parliamentary leaders, including Giolitti, about their ability to form a government. All had declined, seeing the shift of opinion towards intervention as decisive. This afternoon the king summons Salandra to Villa Savoia, and meets the politician at the gate with a simple declaration: 'It is necessary that you withdraw your declaration.' Salandra agrees, and his cabinet formally returns to office, and Italian entry into the war is now a certainty.
- In the Mediterranean the Austro-Hungarian destroyer Triglav successfully tows the German coastal submarine UB7 through the Straits of Otranto, evading the Entente blockade, and the latter then makes its way eastward towards the Dardanelles.