“Police had to interpose themselves between the rival groups.”

“Thus, for example, a liver that is palpable may not be detected by percussion, if, as occasionally happens, a segment of colon is interposed between the liver and the abdominal wall.”

“… a solid line of police in riot gear interposed itself between the trade ministers and the crowd of protesters.”

“I hate to interpose, but could you tell me what you meant by that last remark?”