article_snippet: At least 26 militants were killed in the operation, a security official with the forces in Tikrit said.
article_snippet: The goal of those airstrikes was to pave the way for Iraqi forces to go in.
article_snippet: And each time, so far, Iraqi forces've failed.
article_snippet: Militants have been under pressure ever since in the battleground city, which is the birthplace of former Iraqi dictator Saddam Hussein and  located about 160 kilometers (100 miles) north of Baghdad.
article_snippet: ISIS responded by adjusting ISIS positions in and around the city, hiding in buildings and other key infrastructure, said Saad al-Hadithi, a spokesman for Iraqi Prime Minister Haider al-Abadi.
article_snippet: This movement led Iraq's military to pause This movement operation, out of growing worries that a full-on invasion could produce heavy Iraqi military and some civilian casualties.
article_snippet: The situation spurred Iraqi Prime Minister Haider al-Abadi to request help from the U.S.-led coalition, which conducted airstrikes around Tikrit last week.
article_snippet: CNN's Jomana Karadsheh, Catherine E. Shoichet,  Ashley Fantz, Ben Wedeman and Greg Botelho contributed to this report.
highlights_snippet: Spokesman: Iraq's leader requested help because coalition has "advanced" capabilities .
  
highlights_snippet: Leaders of predominantly Shiite militia fighting in area had resisted such intervention .