In what years were non-Muslims the fiercest in war against Muslims?

[wgirl]

I know that the Makkah period was relatively peaceful and that the Madinah period was relatively troubled with warfare. Which years can one say were the worst in terms of the hostilities and warfare that the Muslim community faced from non-Muslim groups?

Is the day the Muslim community moved to Madinah considered 0 after Hirja or 1 after Hijra?

I ask this because the word Kāfir, which I normally translate as ‘non-Muslim, one who rejects Islam’ in basic English, has a slightly different shade of meaning in the Madinah chapters of the Qurʾān because of the very different context of revelation. Because of the climate of warfare, the word Kāfir almost comes to mean ‘one who is hostile to Islam’, doesn't it? Or are there examples of Kāfirūn who were neutral or non-hostile to Muslims in the Madinah period?

[Nomadic]

The word kafir comes from the word kufr means covered. Denying the truth means covering up the truth and hence the word kafir. It is not an insult but a word that describes those who reject the truth. However thanks to many of our overzealot brother, this brother is now equated as insult. Pathetic really.
Allahualam