Although no large operations took place at the beginning of 1916, there was continual fighting in various parts of the line. The Germans made several attacks on the Yser Canal and at Neuville on the French front, and also attempted minor operations at Givenchy and on the Ypres--Comines Canal. In February the great battle of Verdun commenced, and in spite of heavy losses the Germans made some progress, capturing Haumont Wood and Village. Large masses of men were employed, and there was severe fighting at Bethincourt and Le Mort Homme. The Germans persisted in their attacks and captured Avocourt Wood, but the French stubbornly held their ground. At the end of March the British Army made a successful attack at St. Eloi, and penetrated the first and second German line of trenches, but lost the Vimy Ridge, a position of some tactical importance. The Russians won a great victory in the Caucasus and drove the Turks in disorder towards Erzeroum, which they captured soon afterwards. The position of the British Force on the Tigris was giving great anxiety, and the Turks claimed to have completely surrounded it. In March Portugal joined the Allies, and declared war on Germany and Austria. In Africa the Cameroons campaign was completed with the surrender of the German garrison at Mora Hill. General Smuts advanced against the Germans in the Kilimanjaro area, and a week later gained further successes west of Taveta. The United Kingdom resorted to conscription, and the Military Service Act was passed in the House of Commons. [Sidenote: April, May, June.] On the British front the Germans launched determined but unsuccessful attacks at Ploegsteert, and there was fighting on the Vimy Ridge and between Loos and La Bassée. The struggle at Verdun continued with unabated fierceness, and Mort Homme and Fort Douaumont changed hands several times. The battle of Jutland was fought, and the British Grand Fleet had an opportunity of meeting the German High Seas Fleet. The British Cruiser Squadron had most of the fighting, as the battleships did not come into action till late in the evening. The losses were heavy on both sides, and the German Fleet fled back to harbour claiming the victory. Serious disturbances broke out in Ireland, and martial law was proclaimed in Dublin. The headquarters of the rebel Sinn Feiners was occupied after much street fighting, and the ringleaders were caught, tried by court-martial, and shot. In Mesopotamia the troops sent up to relieve the British Force at Kut-el-Amara failed in their attack on the intervening Turks, and on April 29 General Townshend and a force of native and Indian troops surrendered. President Wilson warned the Germans that if they persisted in their indiscriminate sinking of neutral vessels, he would have no alternative but to break off diplomatic relations.