The Central Powers advance towards Moldavia was hampered by bad weather and poor infrastructure and as a result hostilities were only resumed in the summer of 1917. A plan to break through the lines of Field Marshal August von Mackensen's German forces was elaborated, requiring a dual offensive from the First Army in the Nămoloasa sector and the Second Army in the Mărăşti sector. Although the Nămoloasa offensive was canceled, the Second Army's attack led to the Battle of Mărăşti, which ended with the Romanians' victory after creating a breach 30 km wide and 20 km deep in the front, after nine days of fighting, between 22 July and 1 August. Field Marshal von Mackensen launched a counterattack on 6 August 1917, which led to the Battle of Mărăşeşti; the Romanians managed to resist against repeated German attacks until 8 September, when both sides ran out of fresh units. Victory came at a great cost, with the Romanians losing over 27,000 men, including 610 officers; the Germans lost 47,000 men. The motto of the Romanian Army during the battle was "Pe aicea nu se trece" (English: "You shall not pass"). At the same time, German and Austro-Hungarian forces launched an attack in the Oituz valley against forces of the Second Army. The Battle of Oituz lasted from 8 August to 22 August 1917 and ended with a Romanian strategic victory, as the Austro-Hungarian forces failed to break through into the Trotuş Valley.