The offending History.com article in question (big surprise there)

As I'm sure many of you may be aware, /u/elos, myself, and countless others have been fighting the good fight against Reddit-based WWI Badhistory. This is my first ever /r/badhistory post, and surprise surprise, it concerns History Channel and the Somme. Much of what I am posting is in this /r/history thread, but since /u/HockeyGoalie1 suggested this might sit well with fellow Shills of Big Historiography, 'Dux gon give it to ya'.

When World War I broke out in August 1914, great throngs of British men lined up to enlist in the war effort. At the time, it was generally thought that the war would be over within six months.

There is no evidence that the 'War would be over by Christmas' was ever held in wide belief in 1914; so far as Adrian Gregory can tell in his work The Last Great War, it seems to have sprung up in later years, as a way of lampooning such optimism. As I note in this /r/AskHistorians answer, there was serious planning in Germany with regards to the likelihood of a prolonged struggle before 1914. Kitchener called up the new armies with the knowledge that they wouldn't be ready until 1915 at the very least, and he didn't expect the British Army to be making any major effort until at most 1916, more likely 1917 (in ol' K of K's words, "The real war won't start until 1916").

On the Western Front–the battle line that stretched across northern France and Belgium–the combatants had settled down in the trenches for a terrible war of attrition.

Attrition did not become the aim of Allied strategy until the Inter-Allied Conference at Chantilly in November, 1915. The stated goal of the General Allied Offensive next year would be the 'destruction of the enemy's armies', specifically those of the German and Austro-Hungarian Empires. For more info, I recommend William Phillpott's books Bloody Victory and War of Attrition.

With the aim of raising enough men to launch a decisive offensive against Germany, Britain replaced voluntary service with conscription in January 1916, when it passed an act calling for the enlistment of all unmarried men between the ages of 18 and 41.

This had more to do with the fact that compulsion under the Derby Plan wasn't working, and Britain needed to institute a more organized system of providing the Army with manpower. Conscription, which was already utilized by all the major combatants, would weed out those men that were needed for vital war work, and thus ensure that industrial and military demands could be met efficiently. As Richard Holmes points out in Tommy, many conscripts would argue that they would have volunteered sooner or later, but conscription made that choice for them.

Near the end of June, with the Battle of Verdun still raging, Britain prepared for its major offensive along a 21-mile stretch of the Western Front north of the Somme River.

It was not a solely British offensive; British 4th Army under Henry Rawlinson would attack along a 20 km front north of the Somme, but south of the Somme Emile Fayolle's French 6th Army would attack along a 10 km front. It was a joint offensive, coordinated by Ferdinand Foch, aimed at inflicting heavy losses on the German Army, and driving it from it's positions in Picardy, centered on the Thiepval-Combles Massif, Lassigny and the Flaucourt Plateau. It would also have the immediate effect of forcing the Germans to disengage from their offensive at Verdun, and give the French Army time to recuperate and counter-attack.

For a week, the British bombarded the German trenches as a prelude to the attack. British Field Marshal Douglas Haig, commander of the British Expeditionary Force, thought the artillery would decimate the German defenses and allow a British breakthrough; in fact, it served primarily to remove the element of surprise.

Haig was C-in-C British Armies in France and Flanders; General Sir Henry Rawlinson was GOC 4th Army. Rawlinson was the one who decided on a methodical bombardment, and it made sense. Haig, for his part, wanted a short, hurricane barrage, but with the state and quantity of British shells and artillery, in tandem with the length of front and depth of enemy defences, this was unfeasible. Moreover, there was really no point in operational surprise on the Western Front: allied papers tracked the build-up, the Somme sector was where Franco-British lines met and thus the only place a joint offensive could be launched; the build-up requires for an offensive was obvious to the enemy; a methodical bombardment would ensure that the enemy's positions were thoroughly shelled, and would spare the British guns from excessive wear in a short time, which a hurricane bombardment would have entailed. There were plenty of officers and soldiers sceptical of the bombardment, and even it had worked, there still would have been bloody fighting ahead. It truly amazes me that the actions taken by the enemy don't seem to factor in when 'what went wrong on July 1st' comes to mind. For the view from 'the other side of the hill', consult Through German Eyes by Christopher Duffy and German Army on the Somme 1914-16 by Jack Sheldon.