Actually, the American administration was put in a real dilemma as far as the WWI is concerned. The so called American neutrality has its roots back into history since the Monroe doctrine when the, then, American president pointed out that America wouldn't intervene unless the American hemisphere is at stake. This doctrine evolved throughout history and became better framed in what is known nowadays the American isolationism. This belief is factually a little hard to determine or to define in a strict way since it has been subject to constant shifts and modifications. It depended in a number of occasions on the interests and the political strands followed by the consecutive American administrations. Whenever it is perceived i as an "urgency" to declare war against an enemy or to participate in a conflict, the USA proved to be ready at anytime to send its troops to the battlefield. That was clearly proved and accounted for by clear and substantial evidences all along the short American history. one of the instances where the US administration broke up the tradition of isolationism was during the WWI. It is believed that the First World War was reckoned by the American gvt as a purely European conflict wherein America was not involved neither directly nor indirectly. However, there were some signs and indicatives raising doubts and questioning the sincerity of the American neutrality. Since 1915, the US proceeded to cut its economic relations with Germany and directing all its economic strength to boosting the British collapsing economy and supplying it with the various war needs. Even worse, when the American ships, sailing only and mostly for economic and commercial ends, were shot and sunk in the mediterranean, the American gvt kept silent and tolerated the aggressive moves taken by the British. That heralded clearly and declaredly that the USA sided with the Allied troops against the central powers despite all the economic and diplomatic irreversible repercussions inflicted on it due to its stance. Germans were vigilant and shrewd enough to get the msg and to work on forcing the American troops to take part in true terms in the war. This can be explained by numerous factors mainly the notorious special relations holding the American people with its British counterpart. As it's widely known, the bulk of the settlers of the New World were descendants of British families which helped hold the tie with their ancestors and share a set of interests and strategies. Briefly, the American neutrality has been caught into a kinda tide and ebb fashioned and handled swiftly and smoothly according to the well being and the interests of the nation and of Americans themselves away from being absolute and blindly pro-unconditional-non-entanglement.
I will contribute a two part answer to this question.
The tactical reason that troops were sent to this area was a foolish plan designed by Churchill, a mid level English military leader in 1915.
The plan was to occupy the area, force the Turkish army to abandon their largest city, Istanbul/Constantinople. This would cut off all supply from Europe, including Germany, to Central Power armies in Asia minor, Syria, Arabia, etc. Thus, these areas could quickly be overrun by Allied armies and a great victory achieved. Of course, even a cursory review of a map reveals that the logistical support for such a campaign would be daunting. Distances were huge. German/Turkish support was readily available via rail. The invasion beaches were poorly selected. The weather was awful. The Turks proved excellent fighters and quickly contained the British positions. German submarines in the Mediterranean shot up many Allied warships in the close quarters. Ultimately the entire fiasco was cancelled by the Allies and the survivors withdrawn. The area remained under Central Power control for the wars duration. Churchill, rightfully, lost much prestige over this campaign. However, he learned nothing from the disaster. In 1941 he began planning again for a campaign of a similar fashion. This new plan was to invade.....Italy. Again, the troops got bogged down in rough terrain and terrible weather. Again, the effort in this peripheral arena drained resources that were critically needed on other fronts, thus extending WWII as it had WWI.
My second answer is in regards specifically to the use of Australian troops in this battle. It is well known by most history buffs that the English love to use 'colonials' for their heaviest fighting. The English may take the credit for victory later, but they prefer that most casualties be in the column of others. Thus they used Australians to fight in Turkey in 1915, Canadians to 'test' invade France in 1942, Canadians and Americans in 1944 to do almost all the heavy fighting in Normandy, and Americans to invade Italy in 1943 (even when the American leadership opposed the Italian campaign as a waste and irrelevant to the main issue). Thus as you read details on various 'English' engagements in WWI and WWII, you will note that very often the troops involved are Scottish, Indian, South African, Australian, New Zealanders, etc.
To support to the British Empire during World War One.
However the colonial British ( Australians ) were not committed to the fighting in Europe at the time the British government decided to attempt to knock Turkey out of the war as Turkey had sided with Germany and was a threat to British interests in the middle east . It was also considered to a way of supporting Russia as Russia was fighting against the Germans .
The plan was to attack the capital of Turkey by using the British and French navies to sail through the Dardanelles ( a narrow waterway leading to the Turkish capital ) and shell Istanbul thereby forcing the Turks to surrender .
That plan failed because of the fierce resistance of the Turks on each side of the Dardenelles and mines which sank many of the ships .
A new plan was devised to land troops and capture the forts blocking the way .
French , British and ' Australian' troops landed on the Turkish peninsular near Gelibolu ( Galipoli ) but were held and finaly repulsed by the Turks .
Which meant that the British attempt to knock Turkey out of the war had completely failed . The British and allied forces retreated and the survivors were sent to fight in Europe .
Germany attacked France by invading through the north of Belgium.
Poland was attacked by Germany to start world war 2.