A decapitation strike, and operations deep into enemy territory to capture their leader, must be a completely one-sided affair. You need to suppress the enemy the entire time to succeed.
If a decapitation strike turns into a stalemate or a drawn-out siege, there's no doubt — it's already a failure.
And if it results in heavy losses without breaking through, then it's undeniably a disastrous defeat.
It's acceptable to sustain some casualties, but the momentum must be overwhelming. The enemy's defenses need to collapse quickly, and then it's all about pursuit. Whether they're caught or not is secondary; the key is to crush their will and send them fleeing in panic.
But if the enemy has superior stamina, can keep sprinting through the jungle, and your pursuers, after hiking for hours, are absolutely spent... well, that's when things get tricky.