One important key to winning is to start off strong. This can be done by getting a hospital as soon as possible. If you can't then get extra space for new survivors. The next most building to have is a school. that is very important because you one leader and everyone else should be a soldier. The only exceptions are the scientists. When it comes to scientists, only have as many as neccessary. Another great tip is to scout as many areas as possible. Also, never do a mission that has any danger. The same applies to your fort, horde or no horde. That's just in case the bikers or kill squad pays a visit. If you want to hold off hordes then stop them before they start. This is done by killing zombies anywhere possible even if it's pointles to do so otherwise. A pointer that may or may not help is to leave a soldier or two to remain idle. In the same context on the possibility of being helpful is to always be on some mission everywhere so that zombies can't overrun them. The only time when you shouldn't is when there's a horde on the way...
I think on the harder level - you should take more gambles on dangerous missions. When I played on "harder" - I consistently sent soldiers into mission where the danger level is between 7% and 15%. If I recall correctly - only once in a great while that someone died. On "harder", it is very important to be able to expand your base as quickly as possible - at the same time you need more builders to quickly reclaim any buildings.
Time IS everything in harder level.... coz the hordes will get stronger and stronger, and you need to reclaim as many mall, police station, Walmart ASAP for defense, and of course BIG farms, apartments/trailer parks, hospitals, schools, research centers... etc.
Expand your base at all cost...! Forget about scavengers altogether.
On hardest levels not hordes kill you(on nightmare i never saw hordes more than 1500) but average zed's spawn rate. it's more than 250 per day - even if you use 100 soldiers(and it is really annoying to send EACH soldier EACH 2 turns on kill mission) on kill missions they can't kill more than 100-150 zeds. If you want to beat nightmare, first target - hospital. second - win with curing zombeism
Also some tricks: If you have apartments near starting area - you must reclaim it asap. Then send all useless scientists-scavengers on transforming you starting suburbs into farms.While transforming try to gather as much survivors as you can. When transformation will be finished, you can have around 20 people with almost non-negative food income.(sure, you will hit cap, but with this amount you can reclaim another houses. Maybe you will lost possibility of "lone gunman", but i don't think that you will have enough hapiness - parties is key to prevent riots and suicides)
You need more defenses for the base and more food. Taking the Town Hall or finding the antidote will win the game(but the antidote has no use since you need 4 Scientists and Labs) You need the hospital really and more apartment and farms. Hordes will come sooner so be ready and have your defenses strong. At least send 2-4 Soldiers to kill the horde and 2 only for scout missions (or possibly one) Never mind the Scientists once they finished their job of all the research. convert them to soldiers and scavengers also will soon be worthless. Builders are somewhat useful along with the leaders. You need to kill the zombies before they attack you and that would be a good defense against them. Convert the not useful buildings to apartments or other things.
Just keep getting food and people at the beginning and don't worry about space then after u've got a lot of soldiers send them to take over places while they're doing that just scavange for food and recruit more people.
i like your strategy over all, but i find it strange that you think that you should not send your guys out if there is any danger at all. i understand if it is like 30%-ish or more, but if it is rather low, namely 1-25%, why wouldn't you conduct a mission, as it is highly unlikely that you will lose a guy.
