Each month, hundreds of trucks heavy with fuel, cement and other goods cross a plowed no man’s land between Egypt and the Gaza Strip — and Hamas becomes stronger.

Hamas collects tens of millions of dollars a month in taxes and customs at the crossing in the border town of Rafah, according to estimates. The funds help it operate a government and powerful armed wing while international aid covers most of the basic needs of Gaza’s 2 million residents.

That this is happening with the quiet acquiescence of Israel, which considers Hamas a terrorist group, might come as a surprise.

Israel says it works with Egypt to supervise Rafah in return for quiet. The opening of the crossing “was a common interest for all parties to ensure a lifeline for Hamas that would enable it to maintain calm in Gaza and prevent an explosion,” said Mohammed Abu Jayyab, an economist and editor-in-chief of a business daily in Gaza.

But there’s more to it. After surviving four wars and a nearly 15-year blockade, Hamas has only become more resilient, and Israel has been forced to accept that its sworn enemy is here to stay.