So as you see kidnapping for ransom is not terrorism, it's a crime. Killing a leader considered as enemy in war area it's not a terrorism.
Kidnapping and then terrorizing the victims is terrorism, just like those people kidnapped in Iraq and made to do videos pleading for their lives. Yes many were released when countries like Italy paid up. Assassination, especially with a bomb in a crowded stadium that got a lot of civilians is terrorism.
Sentence 1. For your information terrorism is a very big factor in all guerrilla wars.
Sentence 2. Guerrilla warfare is the favorite tactic of terrorist organizations when they're brought to a fight.
Simple example of that logic:
1. All cats are animals.
Other way round:
2. All animals are cats.
Assassination, especially with a bomb in a crowded stadium that got a lot of civilians is terrorism.
You want to tell me that Israel lunched some terrorist strikes? Many assassination of islamic leaders with help of air force were succesfull - target destroyed. But there was some collateral damage. Few civilians died.