The most intense Sunni insurgent activity takes place in the cities and countryside along the Euphrates River from the Syrian border town of al-Qaim through Ramadi and Fallujah to Baghdad, as well as along the Tigris river from Baghdad north to Tikrit. Heavy guerrilla activity also takes place around the cities of Mosul and Tal Afar in the north, as well as the "Triangle of Death" south of Baghdad, which includes the "-iya" cities of Iskandariya, Mahmudiya, Latifiya, and Yusufiya. Lesser activity takes place in several other areas of the country. The insurgents are believed to maintain a key supply line stretching from Syria through al-Qaim and along the Euphrates to Baghdad and central Iraq, the Iraqi equivalent of the Ho Chi Minh trail. A second "ratline" runs from the Syrian border through Tal Afar to Mosul.