S13·E10 1915 - The Deadliest Year of WW1?

Episode recap

Topic: Episode recap for The Great War S13E10 (1915 - The Deadliest Year of WW1?).
Constraints:
Write ONLY verifiable facts from the provided SYNOPSIS and SOURCES.
No inventing/guessing titles, names, dates, counts, awards, ratings, etc.
Original, neutral, encyclopedic prose.
Plain text only (no markdown, no asterisks, no headings, no bullet points).
Word count: 280-380 words.
If details are missing, omit rather than guess.
Synopsis: 1915 was the first full year of the First World War. It expanded carnage to new fronts and saw massive battles along the ones from 1914. The Western Front became an entrenched stalemate that neither Germany nor the Allies could break. In the East, Germany and Austria-Hungary beat back Russia and crushed Serbia with the help of a new ally. In Gallipoli, the Allies failed to defeat the Ottomans, but elsewhere the Turks were losing.
Source [1]: Series title: The Great War (2014). Cast: Indy Neidell.
Source [2]: Cast: Indy Neidell, Jesse Alexander, Othais McCarthy, Tsar Nicholas II. Series follows events week by week.
Source [3]: Season 13 premiered Jan 16, 2026.
Source [4]: Wikipedia mentions a 26-episode documentary series from 1964, but the user is asking about S13E10 of the 2014 series (implied by the context of Indy Neidell). Correction: I must be careful. Source [4] describes a 1964 series. Source [1], [2], [3], and [5] refer to the 2014 series. The prompt asks for S13E10.
Source [5]: Season 13 has 10 episodes. Indy Neidell stars.
The episode focuses on the year 1915, which marked the first full year of the First World War.
During this period, the conflict expanded to new fronts and included massive battles along the fronts established in 1914.
On the Western Front, the war transitioned into an entrenched stalemate that neither the Allies nor Germany could break.
In the East, Germany and Austria-Hungary defeated Russia and crushed Serbia, aided by a new ally.
In the Gallipoli campaign, the Allies were unsuccessful in their attempt to defeat the Ottomans. However, in other areas, the Turks were experiencing losses.
The series The Great War features Indy Neidell, Jesse Alexander, and Othais