Editing Brusilov offensive (section)

==Breakthrough==
On 4 June, the Russians opened the offensive with heavy artillery fire. Alexander Winogradsky's artillery brigade used 76mm guns to open 24 breaches in the Austro-Hungarian defenses, coordinated in advance with the infantry commanders. Winogradsky wrote, this was followed by a "creeping barrage in front of the assault infantry...while the 152mm howitzers and 122mm guns attacked hard points." This was followed by attacks by infantry in Kaledin's 8th Army, [[Vladimir Viktorovich Sakharov]]'s 11th Army, [[Dmitry Shcherbachev]]'s 7th Army, and [[Platon Lechitsky|Lechitsky's]] 9th Army.<ref name=rlg/>{{rp|140–146}}

On 5 June, according to Prit Buttar, "...the Russian gunners resumed their careful demolition work of the defences of Joseph Ferdinand's [[4th Army (Austria-Hungary)|4th Army]]... After two days of careful artillery fire and infantry attacks, Kaledin was confident their success was close. His troops had [[Battle of Lutsk|overrun]] both the first and second lines of enemy defences, and had inflicted heavy losses on the Austro-Hungarian 4th Army." Ferdinand was almost out of artillery ammunition, had used all of his reserves, and was forced to seek help from [[Alexander von Linsingen|Linsingen]]'s [[Army of the Bug]] to the north.<ref name=rlg/>{{rp|150–152}}

By the end of 6 June, The X and UU Corps, plus [[Sándor Szurmay]]'s Corps, of the Austro-Hungarian 4th Army, had been pushed back to the [[Styr]] and beyond, while Kaledin's XL and II Corps pushed onward to Lutsk. By the end of 7 June, the 4th Army retreat was unstoppable, with many elements of the X Corps surrendering when caught against the river, or casualties in attempts to cross. 4th Army supplies abandoned in Lutsk went up in flames as the Russians occupied the town. Further south, Pflanzer-Baltin's [[7th Army (Austria-Hungary)|7th Army]] was pushed back to the [[Strypa]], as Shcherbachev's Seventh Army captured [[Yazlovets|Jazłowiek]].<ref name=rlg/>{{rp|155–165}}

The first major attack was against the 117,800 strong Austro-Hungarian 4th Army, in the northernmost sector of the front.{{sfn|Watson|2015|p=303}} The initial attack was successful, and the Austro-Hungarian lines were broken, enabling three of Brusilov's four armies to advance on a wide front (see: [[Battle of Kostiuchnówka]]). Within four days of the offensive, the Austro-Hungarian 4th Army saw its strength fall by nearly 70 per cent, from 117,800 men to just 35,000. The southern sector was held by the Austro-Hungarian 7th Army, which by 8 June lost 76,200 of its 194,200 soldiers.{{sfn|Watson|2015|p=305}}

Archduke Joseph Ferdinand was replaced by [[Karl Tersztyánszky von Nádas]] as 4th Army commander, and Hugo Martiny was replaced by Smekal as X Corps commander. After four days into the offensive, Buttar states, "Brusilov's revolutionary tactics had been stunningly successful: artillery had been used with a precision that was unprecedented; infantry had worked their way close to the defences before launching their attacks; and those attacks had not used the traditional lines of men that were so easy for machineguns and defensive artillery to destroy."  However, Brusilov was informed by Alexeyev that Evert's West Front would not be able to commence their attacks before 18 June.  Meanwhile, Linsingen ordered [[Friedrich von Bernhardi]] to gather German forces for a counterattack.<ref name=rlg/>{{rp|153–165}}