1970–75 war and the evacuation of the cities had destroyed or idled most industry, small contingents of workers were allowed to return to the urban areas to reopen some plants. Like their Chinese counterparts, the Cambodian communists had great faith in the inventive power and the technical aptitude of the masses, and they constantly published reports of peasants' adapting old mechanical parts to new uses. Similar to Mao's regime, which had attempted unsuccessfully to build a new steel industry based on backyard furnaces during the Great Leap Forward, the Khmer Rouge sought to move industry to the countryside. Significantly, the seal of Democratic Kampuchea displayed not only sheaves of rice and irrigation sluices, but also a factory with smokestacks. Foreign relations The Democratic Kampuchea regime maintained close ties with China, its main backer, and to a lesser extent with North Korea. In 1977, in a message congratulating the Cambodian comrades on the 17th anniversary of the CKP, Kim Jong-il congratulated the Cambodian people for having "wiped out counterrevolutionary group of spies who had committed subversive activities and sabotage". On taking power, the Khmer Rouge spurned both the Western states and the Soviet Union as sources of support. Instead, China became Cambodia's main international partner. With Vietnam increasingly siding with the Soviet Union over China, the Chinese saw Pol Pot's government as a bulwark against Vietnamese influence in Indochina. It is estimated that at least 90% of the foreign aid which the Khmer Rouge received came from China, and in 1975 alone, at least US$1 billion in interest-free economic and military aid came from China. The relationship between the Chinese and Cambodian governments was nevertheless marred by mutual suspicion and China had little influence on Pol Pot's domestic policies. It had a greater influence on Cambodia's foreign policy, successfully pushing the country to pursue rapprochement with Thailand and open communication with the U.S. to combat Vietnamese influence in the region. After Mao died in September 1976, Pol Pot praised him and Cambodia declared an official period of mourning. In November 1976, Pol Pot travelled secretly to Beijing, seeking to retain his country's alliance with China after the Gang of Four were arrested. From Beijing, he was then taken on a tour of China, visiting sites associated with Mao and the Chinese Communist Party. While Democratic Kampuchea held Cambodia's UN seat and was internationally recognized, only the following countries had an embassy