Well, Tanzania is lucky to be surrounded by friendly countries (Kenya, Uganda) or countries that are too poor to wage a war (Mozambique, DR Congo), or countries that are battle weary (Rwanda, Burundi). Did you mean Uganda has never waged a war on Tanzania, how did end.? As for Kenya, nobody is stopping you, go ahead and wage a war on Tanzania, be even hostile to Tanzania if you want. The Tanzania i know, will never start any agression on anyone given the good land and abundant resources..we wait others to start, say if you annex even an inch of Tanzania..we know you need our northern tourist circuit for your tourism business..your favorite!
Kenya has Somalia as its neighbour, a lawless state with extremists running around. Ethiopia has historically been a friendly country, except in pre-colonial periods when Ethiopian tribes (Sidam, Afaan) periodically crossed Abyssinian borders to blood their spears. But its not a country to be trusted. It has 78 million mostly poor people hungry for resources. So, you can imagine the temptation they would have if Kenya discovered oil in Northern Kenya. It makes sense to arm yourself, if only for deterrence purposes.
By the way, Southern Sudan is another wild card. Most people there have known nothing but war all their lives. Uganda sometimes behaves as if Kenya is their enemy. So, probably the only country Kenya regards completely harmless is Tz. There's a rumour though that half of Tanzanian Army is armed with sticks, not guns, Luhehez. Are you out of your mind? You should be using your behind for thinking, maybe you are fitted with an artificial brain!
BTW, I think Tanzanians should be outraged that their government spends so little for defense purposes. Investors tend to develop cold feet on the prospects of investing in places where security is not guaranteed. What if the Somali pirates one day looted Dar's shops? They are becoming more mobile these days. Plus, TZ is one of the countries in the Nile Basin Initiative. The talks have been slowed down these days with both Sudan and Egypt threatening war on anyone who jeopardizes Nile waters. The country (Tanzania) has been threatened by Egypt on its quest to use lake Victoria waters (including those of its tributaries). How can it offer a viable deterrent if it's spending so little in defense? Did Tanzania stop using Lake Victoria, are you aware of Shinyanga mega water project? where water is being pumped form our own Lake Victoria..btw we occupy 51% of it, and you have 9% of it, can you try to annex our share of it, we know you badly need it, but what can you do then?
From strategic point of view, increased defense spending in Kenya makes a lot of sense. Those protesters are just ill informed. Maybe they should reduce the number of children they have so they can pay hospital bills without the governments help.