The effects of a state blocking the Straits of Hormuz, the South China Sea, the Black Sea or the Baltic Sea could seriously threaten international peace and security. Russia too has engaged in numerous incidents with foreign navies in the Baltic Sea and Black Sea. The capability of different ships and aircraft, the differing rules applying in various maritime zones, and the hostile nature of maritime environment itself, combined with the rise in these types of incidents in recent years, require particular consideration. Tensions in the South China Sea appeared to begin in 1974 with military clashes between China and Vietnam over occupation of islands, with substantial loss of life and which occurred again in 1988. At the time of writing, the threat of war between the United States and Iran has been quite high. The United States accuses Iran of making aggressive approaches to its ships in the Gulf.