Political map of Europe & the Mediterranean 20 September 1916 (Somme and Brusilov Offensives): With the Battle of Verdun still raging, British and French forces launched a massive attack on the Germans in the Somme (Battle of the Somme) while the Russians struck in the East (Brusilov Offensive). Both offensives saw huge casualties on each side, but early Russian gains convinced Romania to enter the War (World War I).