Relations between the two entities began in the late 1960s, when leaders of the Sudanese People's Liberation Army, waging an insurrection against the northern government and impressed by Israel's victory in the 1967 Six-Day War, reached out to Israel. Visiting Israel was a punishable offense in Sudan; southerners thus maintained ties with Israel at great personal risk. Israeli envoys also met with regional South Sudanese leaders and initiated an aid programme in the spheres of agriculture and infrastructure development.