You need at least very specialized training in infiltration, poisoning, different unarmed and armed combat styles, wilderness survival...
In the same way that being a programmer requires very specialized training in microprocessor architectures, assembler, design and properties of algorithms, software architectures, standard libraries...
That would be a cotton T-shirt :-)
In the same way that being a programmer requires very specialized training in microprocessor architectures, assembler, design and properties of algorithms, software architectures, standard libraries...
You can teach yourself to code. You can’t teach yourself to fight a dozen armed guards.
Strictly speaking, I’d say you can’t successfully teach yourself to fight a dozen armed guards.
If a ninja has to fight a dozen armed guards, the ninja has already failed :-P