Despite the large amount of money Saudi Arabia spends on weapons, they fear that their traditional inferiority to Iran has not been altered.
With America under President Obama eager for Iran and Saudi Arabia to share the region, rather than prepared to defend Saudi Arabia (and the other Gulf states) from Iranian dominance, Saudi Arabia is reaching out to Egypt which has a large and adequate military but is poor:
Saudi King Salman on Friday announced plans to build a bridge over the Red Sea to Egypt, in a lavish show of support for the government of President Abdel Fattah al-Sisi. ...
Following Salman's announcement, representatives of both countries signed 17 investment deals and memorandums of understanding.
A government official had said the deals agreed with Saudi Arabia throughout Salman's visit would amount to about $1.7 billion (1.5 billion euros).
Recall that Saudi Arabia financed Egypt's purchase of two Mistral amphibious warfare ships built by France for Russia but withheld from Moscow because of Putin's invasion of Ukraine.
With enough Saudi money, Egypt would consider requests for military help with more willingness, eh?
And recall that bridges make troop movements much easier to conduct, as Saudi Arabia demonstrated 5 years ago in Bahrain, where the Saudis were worried about Iranian influence.
UPDATE: Well this is interesting. Apparently a money for security deal wasn't enough for the Saudis, who got the islands Tiran and Sanafir thrown in, too:
Egypt's declared intention to hand over control of two strategic Red Sea islands to Saudi Arabia has kicked off a storm of vociferous opposition, laced with stinging satire, and dealt a blow to the pride of many Egyptians at a time when they feel their country is vulnerable and under attack from all sides.
UPDATE: Israel had to go along with the island transfer. Which raises the question of whether this is a triple alliance of Egypt, Saudi Arabia, and Israel.
And America signed off on the deal, too, apparently.
Which makes this more than just a reaction of our allies concerned about our reliability taking initiatives of their own to cope with threats.
I suppose this can be considered our own hedging of bets on whether Iran is really poised to move on from the nuclear deal to become a responsible regional power, as our diplomacy hopes to achieve.
And in bonus territory, the article speculates that a land swap here could make possible land swaps involving Israel, Egypt, Jordan, and the Palestinians.