A knife is often said to be the most vital tool for wilderness survival, and while there is a strong argument for an axe being at least as important and possibly even more important, especially for long term survival in boreal forests, nine times out of ten a survival knife is going to be at the top of most experts kit lists for survival.
A survival knife may be part of a survival kit that includes various tools; such as an axe, saw and multiple knives to give you a larger option for brush clearance and chopping and a smaller option for food prep and camp craft. Alternatively a survival knife might be a so called ‘one tool option’ and need to be large and robust enough to perform some of the tasks normally expected of an axe while still being useful for smaller tasks.