EELuminatus asked for guides and I had some stuff laying around half finished. So I went and finished it. If you want to see EEL's guide then the magical link below will show you it with just a click of your mouse.
https://test-steamproxy.haloskins.io/sharedfiles/filedetails/?id=1586529908

Defender’s Advantage is basically what it sounds like: A number of advantages that the army defending against attack has over the army attacking. Defender’s advantage is the main reason Turtling works as a strategy. It is important to know each specific Defender’s Advantage so that you can use them to their fullest capacity and so you don’t unknowingly give up that advantage when you are attacked.

In Tooth and Tail, the specific Defender’s Advantages are as follows:

Reinforcement Distance: Warrens will keep producing units while you and your foe are fighting and as you both spam the rally button to try and target important things it will call newly produced units towards the fight to act as reinforcements. This is an advantage for the defender because, since the fight is on the defender’s base, newly produced units are immediately able to join in the fighting, whereas the attacker’s army must travel from their warrens to the defender’s base. Depending on the distance between the attacker’s warrens and the defender’s base (this distance is called rush distance)it could take 5 to 20 more seconds for attacker’s reinforcement to join the battle. That might not sound like much, but in a game where units fire once every second, one squirrel could miss out on 20 shots for 40 damage, and it isn’t often it’s just one squirrel reinforcing. Normally reinforcing squirrels come in waves roughly equal in size to the number of squirrel warrens. 4 squirrel warrens means 4 squirrels traveling for 10 seconds (shorter rush distance in this example) would waste 80 damage! Meanwhile the defender’s 4 squirrel spawned on the battleground and gave their 2 DPS over the next 10 seconds for an extra 80 damage over the attacker.

Defensive Structures: Sometimes I will refer to these as just “defenses”. Defensive Structures are more cost effective than units, so in order for your opponent to beat your Defensive Structures they must have an army that costs more than your defenses (or they could use units that counter defenses like ferrets but shhhh). Defensive Structures can only be built in your territory so this makes them a Defender’s Advantage. When placing Defensive Structures, you need to be mindful that they don’t move! This means that if your defenses don’t protect everything then your opponent will just attack the stuff they don’t protect and your defenses will be food that would have been better spent on units that could at least move to where your opponent attacks. You could protect more things with Defensive Structures by building more defenses, but if you find yourself building the Great Wall of Barbwire, you probably should have just built units that can move.

Warren Tanking: Ever see players that put their warrens as far back as possible to try and keep them safe? How about players who build their warrens in front of their pigs? Well it is the players who build them in front of their pigs who are smarter and it is because of Warren Tanking. Units in Tooth and Tail will attack the closest enemy to them so if you keep your army behind or on your warrens, your opponent’s army will get confused and waste damage attacking your warrens instead of your units that are shooting back. Warren Tanking is best done with T1 warren since warrens get more expensive the higher tier they are without gaining more hit points. T1 warrens have the second best hit point to food cost ratio at 50 hit points for every 60 food. Only gristmills have a better ratio at 150 hit points for every 60 food. Units with shorter ranges have a more difficult time taking advantage of Warren Tanking since they have to get closer to attack. Chameleons, moles, and lizards will often run in front of your warren line to engage the enemy, forfeiting their warren protection.

Warren Tanking Addendum - Warren HP Nerf: Patch 1.5.1 nerfed T1 warren hit points from 50 to 34. In response to this, players have started targeting T1 warrens after a big fight to prevent a comeback from their opponent. T1 warren tanking is still viable, but I also advise you to build your first two to four T1 warrens in a safe location.

Warren Tanking Subsection - Mole Warrens: So patch 1.4 introduced a new thingy in multiplayer, but not campaign, called mole warrens. I didn't add them to this guide at first because I thought they would get removed next patch, but then patch 1.5 came and the mole warrens stayed. This means I need to update this guide with a little info on mole warrens. Mole warrens differ from regular T1 warrens in three ways: 1) they can be built outside of your territory, 2) they only take up one tile instead of four, and 3) they have 25 hit points instead of 34. Mole warrens are not well suited for warren tanking for two reasons: First, the hit point to food cost ratio of these warrens is 25/60 or 5/12 which is the same as a T2 warren. While this is a slightly better ratio than a pig, it is much worse than a normal T1 warren which means you will want to put these warrens behind your regular T1 warrens. Second, because the warren only takes up one tile instead of four, only one unit can stand on top of it. This means that your opponents army is less likely to get confused and waste attacks on the mole warrens. Anyways you should treat mole warrens like T2 warrens and build them behind your other T1 warrens to maximize your defender's advantage.

Pigs: Your little piggies have guns and will shoot at any baddies that get too close. With a mighty 1 DPS per pig and 8 pigs per mill you can get up to 8 DPS. That's a cool 4 squirrels worth of damage. Build your warrens or defenses right next to your pigs and not only will they protect your pigs but your pigs will protect them. Pigs have 4 range (the same as a squirrel) so if something out ranges them like a fox or a ferret, don't expect the pigs to shoot at them. If you build something directly infront of your pigs like a T1 warren then keep in mind that any enemies with 4 or greater range can poke at it without getting in range of you pigs. Pig fire power is most useful against units with shorter ranges like moles, lizards, and chameleons. These units need to get close to their targets to attack so you can have your T1 warren tank and your pigs shoot at the same time. Oh and in case you were worried, pigs keep providing food while shooting.

There are more, I could go on all day about them. These are the ones that I wanted to talk about cuz I see that some players don't always know to take advantage of them. I may update this guide and talk about more if I notice players not taking advantage of some other defender's advantage.

If you want to see my other guide then the link wizards shall provide:
https://test-steamproxy.haloskins.io/sharedfiles/filedetails/?id=1586986260