From the largest perspective, for better or worse, a military is a necessary function for a country to survive. Show me a single country with a history longer than 1 year that survived without any form of military service at all...it just doesn't happen.
The Costa Rican standing army was abolished in 1948. See elespiritudel48 (translation) and US department of state articles.
See also List of countries without armed forces.
"Standing armies [are] inconsistent with [a people's] freedom and subversive of their quiet." --Thomas Jefferson: Reply to Lord North's Proposition, 1775. Papers 1:231
"The pioneers of a warless world are the young men (and women) who refuse military service." -- Albert Einstein
Humans in large groups are violent, greedy, and persnickety about others taking the things they own...meaning other groups of violent, greedy, and persnickety humans.
One solution could be to not join such large groups unless temporarily such large groups are required to do something good, e.g. work together to build a barn or dam. I've lived in a commune where nobody was violent or greedy, and while many people are violent and greedy, that doesn't mean that armies (which are almost exclusively used to start violence, and further greed) are wanted or needed by everyone.
I suppose there are "good" wars and "bad" wars as the AC's post seems to claim, but it doesn't mean that the guys doing the fighting, killing, and dying are at fault or are evil in some way.
There are many people who think that causing pain to creatures that can feel pain is unethical, and successfully refrain from it. We think that killing is almost always wrong (self defense has almost nothing to do with modern wars), and that volunteering to be trained to become a paid killer is even worse - in modern warfare about 90% of the people killed are innocent civilians.
We (humans, that is) dehumanize the enemy; everyone does.
See Philip Zimbardo's The Lucifer Effect for examples of how not everyone is unethical and not everyone dehumanizes others.
The old quote "My country. May she ever be right, but right or wrong, my country!" (Stephen Decatur) doesn't just apply to the US...every citizen of every nation should take up that attitude...and try to fix the things that are wrong.
"Citizenship? We have none! In place of it we teach patriotism which Samuel Johnson said a hundred and forty or a hundred and fifty years ago was the last refuge of the scoundrel -- and I believe that he was right. I remember when I was a boy and I heard repeated time and time again the phrase, 'My country, right or wrong, my country!' How absolutely absurd is such an idea. How absolutely absurd to teach this idea to the youth of the country." -- Mark Twain True Citizenship at the Children's Theater, 1907