Here is the full list of all 40 Defend The Highlands achievements.
Kill 1,000 enemies with turnip turrets
Kill 500 enemies with whisky vomit
Kill 1,000 enemies with golf balls
Kill 10,000 enemies
Kill 15 enemies with Nessy in a single match
Kill 1,000 enemies with porridge cannons
Kill 1,000 enemies with haggis catapults
Get 500 kills with Queen Boadicea
Kill 250 enemies with bagpipe artillery
Get 500 kills with William Wallace
Kill 500 enemies with cheese wheels
Defeat a level 6 enemy on level 1 in skirmish mode
Kill 500 Beefeaters
Kill 500 Welsh Sheep Riders
Recruit 1,000 Scotsmen in total
Complete a skirmish match on impossible
Kill 500 Leprechauns
Complete a skirmish match on hard
Get 500 kills with Robin Hood
Kill 500 Posh Englishmen
Complete a skirmish match on medium
Hit 5 enemies with a single artillery strike or haggis
Kill 500 Ancient Briton Warriors
Kill 500 enemies in melee
Complete a skirmish match without towers
Have 5,000 porridge at once
Complete a skirmish match without heroes
Fully upgrade all stats on a single unit
Kill 500 English Cricket Players
Kill 500 Welsh Rugby Players
Kill 1,000 enemies with porridge bowls
Have 50 Scotsmen at once
Have 2,000 gold at once
Get 500 kills with Alfredo
Kill 1,000 enemies
Kill 500 Irish Potato Farmers
Fully upgrade a stat
Recruit 100 Scotsmen in total
Complete a skirmish match on easy
Kill 100 enemies