They would be opposed by the Russian Third Army with eighteen and a half infantry and five and a half cavalry divisions, under General D. R. Radko-Dmitriev. Mackensen was provided with a strong train of heavy artillery commanded by Generalmajor Alfred Ziethen, which included the huge German and Austro-Hungarian mortars that had crushed French and Belgian fortresses. Airplanes were provided to direct artillery fire, which was especially important since ammunition was short on both sides: only 30,000 shells could be stockpiled for the attack. Another significant plus was the German field telephone service, which advanced with the attackers, thereby enabling front-line observers to direct artillery fire. To increase their mobility on the poor roads, each German division was provided with 200 light Austro-Hungarian wagons with drivers. The German Eleventh Army was ready to start artillery operations by 1 May, with the Korps Kneussl deployed southwest of Gorlice, with the XLI Reserve Corps led by Hermann von François, Austro-Hungarian VI Corps led by Arthur Arz, and the Guards Corps led by Karl von Plettenberg, deployed south to north, while the X Corps was held in reserve. Joseph Ferdinand's Fourth Army was deployed north of the Germans at Gromnik. The Russian Third Army was deployed with the X Corps led by Nikolai Protopopov, XXI Corps led by Jakov Shchkinsky, and IX Corps led by Dmitry Shcherbachev, deployed south to north. The battle Falkenhayn moved German Supreme Headquarters, OHL (Oberste Heeresleitung), to Pless in Silesia, an hour's drive from Austrian headquarters. To prevent spying, the local inhabitants were moved out of the buildup area. In the north the German Ninth and Tenth armies made diversionary attacks that threatened Riga. On 22 April, the Germans launched the first poison gas attack near Ypres, divulging what might have been a decisive weapon merely to distract the Allies in the west. Mackensen had ten infantry and one cavalry divisions (126,000 men, 457 light guns, 159 heavy pieces, and 96 mortars) along the length of the breakthrough sector. Facing him were five Russian divisions consisting of 60,000 men but desperately short on artillery. For fire support, the Russians could only count on 141 light artillery pieces and four heavy guns. One of the four burst as soon as the battle began. The Russian supreme commander, the Grand Duke Nicholas Nicholaevitch, learned that Germans had arrived on their flank but did not make a counter-move. On 1 May,