line to be attached to experienced units for instruction: CLXXIV and CLXXIX on 9 March and CLXXXVI (H) on 12 March, all to Estaires with 8th Divisional Artillery; CLXXXIV on 12 March to Steenwerck to join 34th Divisional Artillery. The brigades attached to 8th DA returned to their waggon lines on 23 March while CLXXXIV returned on 24 March. Next day they moved to the St Venant area, where they completed their equipment. The brigades went up for a second period of instruction 2–3 April to 14 April, three with 33rd (Camberwell) Divisional Artillery in the La Bassée area often used to train new arrivals, and CLXXXIV with 38th (Welsh) DA. 39th Divisional Artillery was then deemed ready to take over its own section of the line, and it relieved 38th (W) DA in the Festubert–Givenchy area between 14 and 16 April. Reorganisation The field artillery of the British Expeditionary Force (BEF) was undergoing reorganisation in the light of experience so far in the war. On 21 March the division was ordered to form a brigade of three medium trench mortar batteries (TMBs) under a Divisional Trench Mortar Officer (DTMO). In 39th Division the men were provided by the RFA gun brigades and DAC; X/39, Y/39 and Z/39 Medium TMBs were each equipped with four 2-inch medium mortars. On 20 May the BACs were absorbed by the DAC and on the same day the field brigades were reorganised as three batteries of 18-pdrs and one of 4.5-inch howitzers: CLXXIV Bde: B Bty became A/CLXXXVI, D Bty became B Bty, and A (H)/CLXXXVI joined as D (H) Bty CLXXIX Bde: C Bty became C/CLXXXVI, D Bty became C Bty, and B (H)/CLXXXVI joined as D (H) Bty CLXXXIV Bde: B Bty became B/CLXXXVI, D Bty became B Bty, and C (H)/CLXXXVI joined as D (H) Bty CLXXXVI Bde: joined by B/CLXXIV, B/CLXXXIV and C/CLXXIX, and retained D (H) Bty. Battle of the Somme From April to June the guns concentrated on registering the enemy's front line positions, machine guns posts and observation posts (OPs), shooting at enemy working parties, and firing in support of trench raids. On 29 June the guns began a preliminary bombardment and wire-cutting for an operation against a German position known as the Boar's Head. The small Battle of the Boar's Head on 30 June was a diversion from the 'Big Push' (the Battle of the Somme)