Massive gold deliveries >$1B actually happen fairly often - any time there's a real price discrepancy, someone is moving gold and making money - and $4B in gold isn't all that big; it's ~45 metric tons. You can easily fit that on a single cargo plane, with costs in the low six figures if it wasn't so valuable. At 5 tons per armored truck that's 9 trucks. Brinks does this sort of thing all the time and they used to - still may? have custody of billions in gold of their own. The whole industry operates with "security by obscurity", so you won't get exact details, but the whole thing is a bit lower security than you're thinking. There are police, but not usually military escorts; even with gold between governments military escorts aren't the rule.