Edit: This was more controversial than I had imagined, so I'll summarise my point like this: If your country is invaded, and you and your family are in danger of being bombed or shot, do you believe that you have some special right that says someone else should put their life on the line to protect you, while you sit back and do nothing? Do you think that you, your family, and your society have a better chance of survival if you all work together to defend yourself? Do you think it's fair that someone who has no impact on the decision to resist or capitulate is bound by that decision? My answers are: No, Yes, No. My right to protection hinges on my obligation to contribute to the protection of others. If we are not willing to collaborate to defend ourselves, we cannot consider ourselves citizens of the same state. A child (or other person without voting rights) cannot be bound by the political decision to resist an invasion, since they have no real way of impacting that decision.

Original post

The shitshow that is the IDF aside, 19 year olds are perfectly capable of being soldiers. Call me old-fashioned, but I honestly believe that being an adult with rights (e.g. to vote) in a democratic society also implies obligations to that society, and that the two (rights and obligations) should follow each other.

To be clear, what I mean is this: I live in a society that provides me with a solid social safety net, as well as a right to protection if shit hits the fan. I then think it's reasonable that I'm obliged to contribute to that safety net for others (in the form of taxes or community service), and protection (in the form of military service if shit hits the fan). Basically, it's an "all for one, one for all" mentality. We're all better off standing together, which means that we all take care of each other (via taxes etc.) in peacetime, and protect each other (in the form of military service) if necessary.

Since I believe that these rights and obligations should be balanced, I think it's reasonable that an 18 year old (which has all the rights of any other adult in my country) carries the same obligation as everyone else. It would be unfair if, say, 18-26 year olds got all the rights but none (or fewer of) the obligations. That immediately also opens the door to the question of which groups should bear the burden of the obligations, and which groups get only the rights.

Full disclaimer: I think the IDF deserves to be burnt to the ground. I also think (in general) that invading another country is, almost^1^ without exception, abhorrent.

^1^The exception being when you invade a country in defence of another country that has already been attacked, like when the UK attacked Germany in WWII, in defence of Poland, France, etc. without having been attacked themselves first.