There are a couple of aspects about the Crusades that need to be remembered, or realized:
1) The trigger for the Crusades was a new zealous Muslim regime that closed down the pilgrimage routes to prevent Christians from visiting the holy sites. The new regime was more interested about pure faith than tourist dollars!
2) While the Crusaders were being pushed out of the Holy Land, the Crusade closer to home - in Hispania - proceeded with all due deliberation. Spain was recovered once and for all. [Details below]
“It was not until 1492 that the Emirate of Granada with city of Granada and the Alhambra and Generalife Palaces, the last remaining Muslim territory in al-Andalus, fell in the Battle of Granada to forces of the Catholic Monarchs (los Reyes Catolicos), Queen Isabella I of Castile and her husband King Ferdinand II…”
So just as the Muslim chapter was closing in Western Europe (Austria’s shock was still to come in 1529!), the discovery of the Western World would proceed from secure anchors in Portugal and Spain!
Though the Templars had been disbanded (not convicted) in the early 1200s, the re-named Hispanic branches of the Templars (Poor Knights of the Temple became Knights of Christ) spent the next 300 years slowly recovering their corner of Europe.
Right around the same time that Spain was being permanently recovered, Islam was conquering the “spa” of Asia - - Afghanistan! I think maybe the Europeans did a little better in the comparison!
- Lastly, though the Base 10 math system (triggered by exposure to the practical business math of Muslim merchants) is in modern times frequently referred to as Arabic Numbers, the mathematical system was actually more Indian than Arabic. And as for the orthography of the numbers themselves, from 0 to 9, the only numeral that Europe clearly borrows from the Arabs is “9” !!!
The other numbers, 0 to 8, appear to be novel creations of a few influential European math mavens. Even the wiki article rejects the “trope” or “urban myth” that European numerals are based on how many angles can be found in each number, but as someone who used to write True Arab numbers while working in Kuwait, the perceived plausibility of the unique approach to European numerals (replacing the Roman ones) is quite reasonable. Neither Arab nor Indic numerals look anything like 2 to 8!
0 - the circle has no angles.
1 - has one angle (the Arabic number 1 looks similar, but is based on “curves” than angles,
as confirmed by their 2).
2 - drawn as a “Z”, we can see 2 angles… even when veiled as a backwards “S”.
3 - clearly a number based on 2 internal angles and 1 external one. Ironically, the “3” backwards looks
similar to the Arab “4”.
4 - Visualize the 4 as a 3-sided triangle on a stick, the stick makes the 4th angle!
5 - drawn with straight line segments, the 5 angles are easy to recreate.
6 - a square (which has 4 internal angles, and a bent flat rising above (provides 2 more angles).
7 - the most tortured of the European numerals. For those who wonder where the "short stroke"
running horizontally across the vertical stem of the “7” comes from - this mini-cross easily creates
4 angles, and then either a bent portion above (or another cross piece as a base) provides the
final 7th angle.
8 - the most dramatic of the European numbers… though it is usually drawn as an upright infinity
symbol, it is derived from 2 squares stacked on top of each other: 2 times the 4 angles of each square.
9 - Trouble! Having reached 8 by stacking 2 squares, would anyone be so bold as to put a flag on top
of all that? Apparently not. The 9 was borrowed directly from the 9 used by the Arabs.
All in all, 1 and 9 might be said to be Arabic. Some say our Zero is borrowed from the Arabs, but they
used a levitated dot to indicate the zero place holder. It would take the European mind to see the dot
(a singularity of nothing?), and see its enlargement as a circle, with no visible angles. This becomes
fodder for word play, with the circular egg (or “goose egg”) sometimes representing zero. And the
famous point system of tennis: Love / 15; Love / 30; Love / 40; Winner - - is based on the French
word for egg:
“It is possible that it derives from the French expression for “the egg” (l’œuf) because an egg looks like the number zero.”
The other explanations for the practice are, shall we say, ridiculous.