NAIROBI, Kenya – Signaling a new offensive mindset, international military officials vowed Friday to fight the pirates as swarms of Somalis moved into the waters off East Africa. Four shootouts with pirates showed that high-seas attacks are intensifying with the end of the monsoon season. Nearly half the 47 ships hijacked off Somalia last year were taken in March and April — the most dangerous months of the year for ships in the Gulf of Aden and Indian Ocean. In the most serious skirmish Friday, six pirates attacked a vessel before breaking off and chasing the French fishing boat Torre...