I made some more changes. Could someone please edit it again?
In 1915, the 1st Canadian Division was recognized as a fighting force, for holding their ground against a new type of warfare: chlorine gas. It was at the Battle of Ypres where the Germans released 160 tons of poisonous chlorine gas on a large section of the Western Front. As the thick yellow clouds of chlorine gas drifted over British and French forces, soldiers started to drop dead, and many tried to run from the area.
Luckily, a soldier from the Canadian Lines discovered that by pressing urine-soaked clothes over their noses and mouths the gas would not penetrate their bodies. By the end of the day, there was a four-mile gap between the allied lines.
The Canadian Division worked all day and night to attempt to fill the gap between the allied lines. On April 24, the Germans attacked in an effort to wipe out the enemy once and for all. Another violent attack was followed by a gas assault. This time the target was the Canadians. In a matter of two days, the Canadian Line experienced 2,000 deaths and 3,000 wounded. Even though the Canadian Division suffered so many loses, it was the first time that a small Canadian force caused a major European power (Germany) to withdraw.
2 answers
Luckily, a soldier from the Canadian Lines discovered that by pressing urine-soaked clothes over their noses and mouths the gas would not penetrate their bodies. By the end of the day, there was a four-mile gap between the allied lines.<~~I think "gap in" would work better than "gap between" -- "between" implies a difference between two things.
The Canadian Division worked all day and night to attempt to fill the gap between<~~"in" not "between" the allied lines. On April 24, the Germans attacked in an effort to wipe out the enemy once and for all. Another violent attack was followed by a gas assault. This time the target was the Canadians. In a matter of two days, the Canadian Line experienced 2,000 deaths and 3,000 wounded. Even though the Canadian Division suffered so many loses<~~"losses" not "loses", it was the first time that a small Canadian force caused a major European power (Germany) to withdraw. or ~~> "the first time that a small force, such as this Canadian division, caused a major European power -- in this case, Germany -- to withdraw.
See if that reads OK to you.
??