Israel won wars with countries of the Arab League including the 1948 Arab-Israeli War, the Six-Day War and the Yom Kippur War. Thereafter, Arab countries were incapable of winning wars with non-Arab countries in the 20th century. What reason made defeat of Israel by the Arab countries difficult? Was it because of Israel's ally the US?
Hi there. I'm going to link a lot of my/others' previous answers that I think capture the question, and if you have follow-ups, please let me know!
How Israeli military development began pre-state, and how it progressed (me)
This answer by /u/smileyman gives an overview of how Israel won in 1948.
I lay out the intelligence failures leading to the surprise in 1973 here.
A good answer on how Israel was faring in the war in 1973 and how it won is here, but the user has apparently deleted their account.
The Six Day War is an easier sell in terms of why the Israelis won; a large part of it was the preemptive strike, and the Arab forces having been tricked into thinking it would be easy (outside of Egypt, which as it bore the brunt of the preemptive strike, basically lost its air force almost immediately and thus panicked). That's perhaps the lowest connection to your question, so if you have follow-ups or want more information, I can try to get back to you; let me know if you're unsatisfied.
Notable: post-1973 the Israeli nuclear deterrent and conventional military strength, plus a variety of other subjects (Iran-Iraq War, the Iranian Revolution generally, Cold War detente, etc.) made conflict less realistic.