Everything would be so much easier if war had only one side. Ours, of course.
There you are, drawing up a wonderful plan for the next war, preparing it, training for it, until everything is perfect.
And then the war starts, and to your utmost surprise it appears that there is another side, too, which also has a wonderful plan, and has prepared it and trained for it.
When the two plans meet, everything goes wrong. Both plans break down. You don't know what's going to happen. How to go on. You do things you have not planned for. And when you have had enough of it and want to get out, you don't know how. It's so much more difficult to end a war than to start a war, especially when both sides need to declare victory.
That's where we are now.
How did it all start? Depends where you want to begin.
Like everywhere else, every event in Gaza is a reaction to another event. You do something because the other side did something. Which they did because you did something. One can unravel this until the beginning of history. Or at least until Samson the Hero.