For years, the world's biggest oil producers have clashed over Middle East politics and battled for energy market share.
But their desperate need to rescue oil prices brought them together last year and that partnership was the focus of talks Thursday between King Salman and President Vladimir Putin in Moscow.
It was the first ever state visit by a Saudi monarch to Russia, and both sides were looking to broaden the relationship.
But oil was front and center. Russia and Saudi Arabia have often competed for energy market dominance. They are engaged in an intense battle over who will be the top supplier to China, a major energy importer with an insatiable appetite for crude.
Together they produce about a quarter of the world's oil and last year clinched a deal designed to eliminate a global supply glut, in part triggered by the rapid rise in American production.
The deal between OPEC, led by Saudi Arabia, and several non-OPEC countries including Russia, to curb supply has helped stabilize markets but has yet to boost prices enough to ease the pain for oil-dependent economies.