LOL. Since when war games conducted without pre announcement ?
By your logic Russia should launch hundred of nuclear ICBM to west Atlantic without notification for reason of war game so that US will be off guard.
You need to announce plan to have war game if your intention is really war game. otherwise dont blame your neigbouring enemy if she feel threatened then conduct preemptive strike.
There was NO announcement of war game to Israel at that time when massive military built up around the border while the rhetoric from Arab leaders, including Egyptian President Gamal Abdel Nasser, was often aggressively anti-Israel and was interpreted as signaling an intent to go to war. Nasser's statements, in particular, were viewed as a direct threat to Israel's existence. More over Egypt had blockaded of the Straits of Tiran at that time. Of course Israel couldn't ignore and consider it just simply a war exercise.