| Dates |
Events |
|
| February 23 – April 5
|
The Germans withdraw to the Hindenburg Line.
|
Details
|
| March 13 – April 23
|
Samarrah Offensive, British capture much of Mesopotamia.
|
|
| Throughout April
|
Bloody April. Particularly heavy casualties are suffered by the Royal Flying Corps at the hands of the German Luftstreitkräfte during British air support operations for the Battle of Arras.
|
Details.
|
| April 2–3
|
Australians attack Noreuil.
|
Details.
|
| April 6
|
The United States declares war on Germany.
|
Details
|
| April 9 – May 17
|
Second Battle of Arras. The British attack a heavily fortified German line without gaining any strategic breakthrough.
|
Details
|
| April 9–12
|
The Canadians obtain a significant victory in the Battle of Vimy Ridge, part of the first phase of the Second Battle of Arras.
|
Details
|
| April 9–14
|
First Battle of the Scarpe, part of the first phase of the Second Battle of Arras.
|
Details
|
| April 10–11
|
First Battle of Bullecourt, part of the first phase of the Second Battle of Arras.
|
Details
|
| April 15
|
Battle of Lagnicourt, part of the second phase of the Second Battle of Arras.
|
Details
|
| April 16 – May 9
|
The Second Battle of the Aisne (a.k.a. Nivelle Offensive) ends in disaster for both the French army and its commander Robert Nivelle.
|
Details
|
| April 17–20
|
Battle of the Hills (a.k.a. Third Battle of Champagne), a diversion to the Second Battle of the Aisne.
|
|
| April 19
|
Second Battle of Gaza. The Ottoman lines resist a British attack.
|
Details
|
| April 22 – May 8
|
Second Battle of Doiran.
|
Details
|
| April 23–24
|
Second Battle of Scarpe, part of the second phase of the Second Battle of Arras.
|
Details
|
| April 28–29
|
Battle of Arleux, part of the Second phase of the Second Battle of Arras.
|
Details
|
| April 29 – May 20
|
Series of mutinies in the French army.
|
Details
|
